diff --git a/functions/builtin.go b/functions/builtin.go
index 0d365ca..9f71288 100644
--- a/functions/builtin.go
+++ b/functions/builtin.go
@@ -65,8 +65,8 @@ func registerBuiltinFunctions() {
 	_ = Register(NewToSecondsFunction())
 	_ = Register(NewChrFunction())
 	_ = Register(NewTruncFunction())
-	_ = Register(NewCompressFunction())
-	_ = Register(NewDecompressFunction())
+	_ = Register(NewUrlEncodeFunction())
+	_ = Register(NewUrlDecodeFunction())
 
 	// Time-Date functions
 	_ = Register(NewNowFunction())
@@ -79,8 +79,8 @@ func registerBuiltinFunctions() {
 	_ = Register(NewMinFunction())
 	_ = Register(NewMaxFunction())
 	_ = Register(NewCountFunction())
-	_ = Register(NewStdDevFunction())
-	_ = Register(NewMedianFunction())
+	_ = Register(NewStdDevAggregatorFunction())
+	_ = Register(NewMedianAggregatorFunction())
 	_ = Register(NewPercentileFunction())
 	_ = Register(NewCollectFunction())
 	_ = Register(NewLastValueFunction())
@@ -109,6 +109,7 @@ func registerBuiltinFunctions() {
 	// Expression functions
 	_ = Register(NewExpressionFunction())
 	_ = Register(NewExprFunction())
+	_ = Register(NewExpressionAggregatorFunction())
 
 	// JSON functions
 	_ = Register(NewToJsonFunction())
@@ -144,10 +145,15 @@ func registerBuiltinFunctions() {
 	_ = Register(NewIsObjectFunction())
 
 	// Conditional functions
+	_ = Register(NewIfNullFunction())
 	_ = Register(NewCoalesceFunction())
 	_ = Register(NewNullIfFunction())
 	_ = Register(NewGreatestFunction())
 	_ = Register(NewLeastFunction())
+	_ = Register(NewCaseWhenFunction())
+
+	// Multi-row functions
+	_ = Register(NewUnnestFunction())
 
 	// User-defined functions (placeholder for future extension)
 	// Example: _=Register(NewMyUserDefinedFunction())
diff --git a/functions/functions_analytical.go b/functions/functions_analytical.go
index d57ee39..150946c 100644
--- a/functions/functions_analytical.go
+++ b/functions/functions_analytical.go
@@ -99,9 +99,11 @@ func (f *LagFunction) Result() interface{} {
 		return f.DefaultValue
 	}
 	// 返回当前值之前第Offset个值
-	// 对于数组[first, second, third]，当前位置是最后一个元素
-	// offset=1时返回second（倒数第2个），offset=2时返回first（倒数第3个）
-	return f.PreviousValues[len(f.PreviousValues)-f.Offset-1]
+	// 对于数组[first, second, third]，当前位置是最后一个元素third（索引2）
+	// offset=1时应该返回second（索引1），计算：len-1-offset = 3-1-1 = 1
+	// offset=2时应该返回first（索引0），计算：len-1-offset = 3-1-2 = 0
+	// 索引计算：len-1-offset，即从最后一个元素往前数offset个位置
+	return f.PreviousValues[len(f.PreviousValues)-1-f.Offset]
 }
 
 func (f *LagFunction) Clone() AggregatorFunction {
diff --git a/functions/functions_array.go b/functions/functions_array.go
index 546c43b..b1653df 100644
--- a/functions/functions_array.go
+++ b/functions/functions_array.go
@@ -47,12 +47,12 @@ func (f *ArrayContainsFunction) Validate(args []interface{}) error {
 func (f *ArrayContainsFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	array := args[0]
 	value := args[1]
-	
+
 	v := reflect.ValueOf(array)
 	if v.Kind() != reflect.Slice && v.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_contains requires array input")
 	}
-	
+
 	for i := 0; i < v.Len(); i++ {
 		if reflect.DeepEqual(v.Index(i).Interface(), value) {
 			return true, nil
@@ -79,12 +79,12 @@ func (f *ArrayPositionFunction) Validate(args []interface{}) error {
 func (f *ArrayPositionFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	array := args[0]
 	value := args[1]
-	
+
 	v := reflect.ValueOf(array)
 	if v.Kind() != reflect.Slice && v.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_position requires array input")
 	}
-	
+
 	for i := 0; i < v.Len(); i++ {
 		if reflect.DeepEqual(v.Index(i).Interface(), value) {
 			return i + 1, nil // 返回1基索引
@@ -111,12 +111,12 @@ func (f *ArrayRemoveFunction) Validate(args []interface{}) error {
 func (f *ArrayRemoveFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	array := args[0]
 	value := args[1]
-	
+
 	v := reflect.ValueOf(array)
 	if v.Kind() != reflect.Slice && v.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_remove requires array input")
 	}
-	
+
 	var result []interface{}
 	for i := 0; i < v.Len(); i++ {
 		elem := v.Index(i).Interface()
@@ -144,15 +144,15 @@ func (f *ArrayDistinctFunction) Validate(args []interface{}) error {
 
 func (f *ArrayDistinctFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	array := args[0]
-	
+
 	v := reflect.ValueOf(array)
 	if v.Kind() != reflect.Slice && v.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_distinct requires array input")
 	}
-	
+
 	seen := make(map[interface{}]bool)
 	var result []interface{}
-	
+
 	for i := 0; i < v.Len(); i++ {
 		elem := v.Index(i).Interface()
 		if !seen[elem] {
@@ -181,27 +181,27 @@ func (f *ArrayIntersectFunction) Validate(args []interface{}) error {
 func (f *ArrayIntersectFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	array1 := args[0]
 	array2 := args[1]
-	
+
 	v1 := reflect.ValueOf(array1)
 	v2 := reflect.ValueOf(array2)
-	
+
 	if v1.Kind() != reflect.Slice && v1.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_intersect requires array input for first argument")
 	}
 	if v2.Kind() != reflect.Slice && v2.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_intersect requires array input for second argument")
 	}
-	
+
 	// 创建第二个数组的元素集合
 	set2 := make(map[interface{}]bool)
 	for i := 0; i < v2.Len(); i++ {
 		set2[v2.Index(i).Interface()] = true
 	}
-	
+
 	// 找交集
 	seen := make(map[interface{}]bool)
 	var result []interface{}
-	
+
 	for i := 0; i < v1.Len(); i++ {
 		elem := v1.Index(i).Interface()
 		if set2[elem] && !seen[elem] {
@@ -230,20 +230,20 @@ func (f *ArrayUnionFunction) Validate(args []interface{}) error {
 func (f *ArrayUnionFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	array1 := args[0]
 	array2 := args[1]
-	
+
 	v1 := reflect.ValueOf(array1)
 	v2 := reflect.ValueOf(array2)
-	
+
 	if v1.Kind() != reflect.Slice && v1.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_union requires array input for first argument")
 	}
 	if v2.Kind() != reflect.Slice && v2.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_union requires array input for second argument")
 	}
-	
+
 	seen := make(map[interface{}]bool)
 	var result []interface{}
-	
+
 	// 添加第一个数组的元素
 	for i := 0; i < v1.Len(); i++ {
 		elem := v1.Index(i).Interface()
@@ -252,7 +252,7 @@ func (f *ArrayUnionFunction) Execute(ctx *FunctionContext, args []interface{}) (
 			result = append(result, elem)
 		}
 	}
-	
+
 	// 添加第二个数组的元素
 	for i := 0; i < v2.Len(); i++ {
 		elem := v2.Index(i).Interface()
@@ -282,27 +282,27 @@ func (f *ArrayExceptFunction) Validate(args []interface{}) error {
 func (f *ArrayExceptFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	array1 := args[0]
 	array2 := args[1]
-	
+
 	v1 := reflect.ValueOf(array1)
 	v2 := reflect.ValueOf(array2)
-	
+
 	if v1.Kind() != reflect.Slice && v1.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_except requires array input for first argument")
 	}
 	if v2.Kind() != reflect.Slice && v2.Kind() != reflect.Array {
 		return nil, fmt.Errorf("array_except requires array input for second argument")
 	}
-	
+
 	// 创建第二个数组的元素集合
 	set2 := make(map[interface{}]bool)
 	for i := 0; i < v2.Len(); i++ {
 		set2[v2.Index(i).Interface()] = true
 	}
-	
+
 	// 找差集
 	seen := make(map[interface{}]bool)
 	var result []interface{}
-	
+
 	for i := 0; i < v1.Len(); i++ {
 		elem := v1.Index(i).Interface()
 		if !set2[elem] && !seen[elem] {
@@ -311,4 +311,4 @@ func (f *ArrayExceptFunction) Execute(ctx *FunctionContext, args []interface{})
 		}
 	}
 	return result, nil
-}
\ No newline at end of file
+}
diff --git a/functions/functions_array_test.go b/functions/functions_array_test.go
new file mode 100644
index 0000000..79bdcfb
--- /dev/null
+++ b/functions/functions_array_test.go
@@ -0,0 +1,65 @@
+package functions
+
+import (
+	"testing"
+)
+
+// 测试数组函数
+func TestArrayFunctions(t *testing.T) {
+	tests := []struct {
+		name     string
+		funcName string
+		args     []interface{}
+		expected interface{}
+	}{
+		{
+			name:     "array_length basic",
+			funcName: "array_length",
+			args:     []interface{}{[]interface{}{1, 2, 3}},
+			expected: 3,
+		},
+		{
+			name:     "array_contains true",
+			funcName: "array_contains",
+			args:     []interface{}{[]interface{}{1, 2, 3}, 2},
+			expected: true,
+		},
+		{
+			name:     "array_contains false",
+			funcName: "array_contains",
+			args:     []interface{}{[]interface{}{1, 2, 3}, 4},
+			expected: false,
+		},
+		{
+			name:     "array_position found",
+			funcName: "array_position",
+			args:     []interface{}{[]interface{}{1, 2, 3}, 2},
+			expected: 2,
+		},
+		{
+			name:     "array_position not found",
+			funcName: "array_position",
+			args:     []interface{}{[]interface{}{1, 2, 3}, 4},
+			expected: 0,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fn, exists := Get(tt.funcName)
+			if !exists {
+				t.Fatalf("Function %s not found", tt.funcName)
+			}
+
+			result, err := fn.Execute(&FunctionContext{}, tt.args)
+			if err != nil {
+				t.Errorf("Execute() error = %v", err)
+				return
+			}
+
+			if result != tt.expected {
+				t.Errorf("Execute() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}
\ No newline at end of file
diff --git a/functions/functions_compression_test.go b/functions/functions_compression_test.go
deleted file mode 100644
index b27f285..0000000
--- a/functions/functions_compression_test.go
+++ /dev/null
@@ -1,141 +0,0 @@
-package functions
-
-import (
-	"testing"
-)
-
-func TestCompressionFunctions(t *testing.T) {
-	tests := []struct {
-		name     string
-		funcName string
-		args     []interface{}
-		wantErr  bool
-	}{
-		// Compress function tests
-		{
-			name:     "compress_gzip_valid",
-			funcName: "compress",
-			args:     []interface{}{"hello world", "gzip"},
-			wantErr:  false,
-		},
-		{
-			name:     "compress_zlib_valid",
-			funcName: "compress",
-			args:     []interface{}{"hello world", "zlib"},
-			wantErr:  false,
-		},
-		{
-			name:     "compress_invalid_algorithm",
-			funcName: "compress",
-			args:     []interface{}{"hello world", "invalid"},
-			wantErr:  true,
-		},
-		{
-			name:     "compress_empty_string",
-			funcName: "compress",
-			args:     []interface{}{"", "gzip"},
-			wantErr:  false,
-		},
-		{
-			name:     "compress_wrong_arg_count",
-			funcName: "compress",
-			args:     []interface{}{"hello"},
-			wantErr:  true,
-		},
-		// Decompress function tests
-		{
-			name:     "decompress_invalid_base64",
-			funcName: "decompress",
-			args:     []interface{}{"invalid_base64", "gzip"},
-			wantErr:  true,
-		},
-		{
-			name:     "decompress_invalid_algorithm",
-			funcName: "decompress",
-			args:     []interface{}{"SGVsbG8gV29ybGQ=", "invalid"},
-			wantErr:  true,
-		},
-		{
-			name:     "decompress_wrong_arg_count",
-			funcName: "decompress",
-			args:     []interface{}{"SGVsbG8gV29ybGQ="},
-			wantErr:  true,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			fn, exists := Get(tt.funcName)
-			if !exists {
-				t.Fatalf("%s function not found", tt.funcName)
-			}
-			
-			// 执行函数
-			_, err := fn.Execute(nil, tt.args)
-			if (err != nil) != tt.wantErr {
-				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
-				return
-			}
-		})
-	}
-}
-
-func TestCompressionDecompressionRoundTrip(t *testing.T) {
-	tests := []struct {
-		name      string
-		algorithm string
-		input     string
-	}{
-		{
-			name:      "gzip_round_trip",
-			algorithm: "gzip",
-			input:     "Hello, World! This is a test string for compression.",
-		},
-		{
-			name:      "zlib_round_trip",
-			algorithm: "zlib",
-			input:     "Hello, World! This is a test string for compression.",
-		},
-		{
-			name:      "gzip_empty_string",
-			algorithm: "gzip",
-			input:     "",
-		},
-		{
-			name:      "zlib_unicode",
-			algorithm: "zlib",
-			input:     "你好世界！这是一个测试字符串。",
-		},
-	}
-
-	compressFn, exists := Get("compress")
-	if !exists {
-		t.Fatal("compress function not found")
-	}
-	
-	decompressFn, exists := Get("decompress")
-	if !exists {
-		t.Fatal("decompress function not found")
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			// 压缩
-			compressed, err := compressFn.Execute(nil, []interface{}{tt.input, tt.algorithm})
-			if err != nil {
-				t.Fatalf("Compress failed: %v", err)
-			}
-			
-			// 解压缩
-			decompressed, err := decompressFn.Execute(nil, []interface{}{compressed, tt.algorithm})
-			if err != nil {
-				t.Fatalf("Decompress failed: %v", err)
-			}
-			
-			// 验证结果
-			if decompressed != tt.input {
-				t.Errorf("Round trip failed: expected %q, got %q", tt.input, decompressed)
-			}
-		})
-	}
-}
\ No newline at end of file
diff --git a/functions/functions_conditional.go b/functions/functions_conditional.go
index 2cb94f5..cf44322 100644
--- a/functions/functions_conditional.go
+++ b/functions/functions_conditional.go
@@ -7,6 +7,28 @@ import (
 	"github.com/rulego/streamsql/utils/cast"
 )
 
+// IfNullFunction 如果第一个参数为NULL则返回第二个参数
+type IfNullFunction struct {
+	*BaseFunction
+}
+
+func NewIfNullFunction() *IfNullFunction {
+	return &IfNullFunction{
+		BaseFunction: NewBaseFunction("if_null", TypeString, "条件函数", "如果第一个参数为NULL则返回第二个参数", 2, 2),
+	}
+}
+
+func (f *IfNullFunction) Validate(args []interface{}) error {
+	return f.ValidateArgCount(args)
+}
+
+func (f *IfNullFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
+	if args[0] == nil {
+		return args[1], nil
+	}
+	return args[0], nil
+}
+
 // CoalesceFunction 返回第一个非NULL值
 type CoalesceFunction struct {
 	*BaseFunction
@@ -38,7 +60,7 @@ type NullIfFunction struct {
 
 func NewNullIfFunction() *NullIfFunction {
 	return &NullIfFunction{
-		BaseFunction: NewBaseFunction("nullif", TypeString, "条件函数", "如果两个值相等则返回NULL", 2, 2),
+		BaseFunction: NewBaseFunction("null_if", TypeString, "条件函数", "如果两个值相等则返回NULL", 2, 2),
 	}
 }
 
@@ -72,21 +94,21 @@ func (f *GreatestFunction) Execute(ctx *FunctionContext, args []interface{}) (in
 	if len(args) == 0 {
 		return nil, nil
 	}
-	
+
 	max := args[0]
 	if max == nil {
 		return nil, nil
 	}
-	
+
 	for i := 1; i < len(args); i++ {
 		if args[i] == nil {
 			return nil, nil
 		}
-		
+
 		// 尝试转换为数字进行比较
 		maxVal, err1 := cast.ToFloat64E(max)
 		currVal, err2 := cast.ToFloat64E(args[i])
-		
+
 		if err1 == nil && err2 == nil {
 			if currVal > maxVal {
 				max = args[i]
@@ -122,21 +144,21 @@ func (f *LeastFunction) Execute(ctx *FunctionContext, args []interface{}) (inter
 	if len(args) == 0 {
 		return nil, nil
 	}
-	
+
 	min := args[0]
 	if min == nil {
 		return nil, nil
 	}
-	
+
 	for i := 1; i < len(args); i++ {
 		if args[i] == nil {
 			return nil, nil
 		}
-		
+
 		// 尝试转换为数字进行比较
 		minVal, err1 := cast.ToFloat64E(min)
 		currVal, err2 := cast.ToFloat64E(args[i])
-		
+
 		if err1 == nil && err2 == nil {
 			if currVal < minVal {
 				min = args[i]
@@ -151,4 +173,82 @@ func (f *LeastFunction) Execute(ctx *FunctionContext, args []interface{}) (inter
 		}
 	}
 	return min, nil
-}
\ No newline at end of file
+}
+
+// CaseWhenFunction CASE WHEN表达式
+type CaseWhenFunction struct {
+	*BaseFunction
+}
+
+func NewCaseWhenFunction() *CaseWhenFunction {
+	return &CaseWhenFunction{
+		BaseFunction: NewBaseFunction("case_when", TypeString, "条件函数", "CASE WHEN表达式", 2, -1),
+	}
+}
+
+func (f *CaseWhenFunction) Validate(args []interface{}) error {
+	if len(args) < 2 {
+		return fmt.Errorf("case_when requires at least 2 arguments")
+	}
+	
+	// 参数必须是偶数个（条件-值对）或奇数个（最后一个是默认值）
+	if len(args)%2 == 0 {
+		// 偶数个参数，必须都是条件-值对
+		for i := 0; i < len(args); i += 2 {
+			// 条件应该是布尔值或可以转换为布尔值的表达式
+		}
+	} else {
+		// 奇数个参数，最后一个是默认值
+		for i := 0; i < len(args)-1; i += 2 {
+			// 条件应该是布尔值或可以转换为布尔值的表达式
+		}
+	}
+	
+	return nil
+}
+
+func (f *CaseWhenFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
+	if err := f.Validate(args); err != nil {
+		return nil, err
+	}
+	
+	// 处理条件-值对
+	for i := 0; i < len(args)-1; i += 2 {
+		condition := args[i]
+		value := args[i+1]
+		
+		// 将条件转换为布尔值
+		condBool, err := cast.ToBoolE(condition)
+		if err != nil {
+			// 如果无法转换为布尔值，检查是否为非零/非空值
+			if condition == nil {
+				condBool = false
+			} else {
+				switch v := condition.(type) {
+				case string:
+					condBool = v != ""
+				case int, int32, int64:
+					num, _ := cast.ToInt64E(v)
+					condBool = num != 0
+				case float32, float64:
+					num, _ := cast.ToFloat64E(v)
+					condBool = num != 0.0
+				default:
+					condBool = true
+				}
+			}
+		}
+		
+		if condBool {
+			return value, nil
+		}
+	}
+	
+	// 如果没有条件匹配，返回默认值（如果有）
+	if len(args)%2 == 1 {
+		return args[len(args)-1], nil
+	}
+	
+	// 没有默认值，返回 nil
+	return nil, nil
+}
diff --git a/functions/functions_conditional_test.go b/functions/functions_conditional_test.go
new file mode 100644
index 0000000..8df5a8e
--- /dev/null
+++ b/functions/functions_conditional_test.go
@@ -0,0 +1,105 @@
+package functions
+
+import (
+	"testing"
+)
+
+// 测试条件函数
+func TestConditionalFunctions(t *testing.T) {
+	tests := []struct {
+		name     string
+		funcName string
+		args     []interface{}
+		expected interface{}
+		wantErr  bool
+	}{
+		{
+			name:     "if_null with null",
+			funcName: "if_null",
+			args:     []interface{}{nil, "default"},
+			expected: "default",
+		},
+		{
+			name:     "if_null with value",
+			funcName: "if_null",
+			args:     []interface{}{"value", "default"},
+			expected: "value",
+		},
+		{
+			name:     "null_if equal",
+			funcName: "null_if",
+			args:     []interface{}{"test", "test"},
+			expected: nil,
+		},
+		{
+			name:     "null_if not equal",
+			funcName: "null_if",
+			args:     []interface{}{"test", "other"},
+			expected: "test",
+		},
+		{
+			name:     "greatest basic",
+			funcName: "greatest",
+			args:     []interface{}{1, 3, 2},
+			expected: 3,
+		},
+		{
+			name:     "least basic",
+			funcName: "least",
+			args:     []interface{}{1, 3, 2},
+			expected: 1,
+		},
+
+		// case_when 函数测试
+		{
+			name:     "case_when simple",
+			funcName: "case_when",
+			args:     []interface{}{true, "result1", false, "result2", "default"},
+			expected: "result1",
+		},
+		{
+			name:     "case_when second condition",
+			funcName: "case_when",
+			args:     []interface{}{false, "result1", true, "result2", "default"},
+			expected: "result2",
+		},
+		{
+			name:     "case_when default",
+			funcName: "case_when",
+			args:     []interface{}{false, "result1", false, "result2", "default"},
+			expected: "default",
+		},
+		{
+			name:     "case_when no default",
+			funcName: "case_when",
+			args:     []interface{}{false, "result1", false, "result2"},
+			expected: nil,
+		},
+		{
+			name:     "case_when invalid args",
+			funcName: "case_when",
+			args:     []interface{}{true},
+			expected: nil,
+			wantErr:  true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fn, exists := Get(tt.funcName)
+			if !exists {
+				t.Fatalf("Function %s not found", tt.funcName)
+			}
+
+			result, err := fn.Execute(&FunctionContext{}, tt.args)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if !tt.wantErr && result != tt.expected {
+				t.Errorf("Execute() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}
\ No newline at end of file
diff --git a/functions/functions_conversion.go b/functions/functions_conversion.go
index 23fad7d..ae74673 100644
--- a/functions/functions_conversion.go
+++ b/functions/functions_conversion.go
@@ -1,18 +1,15 @@
 package functions
 
 import (
-	"bytes"
-	"compress/gzip"
-	"compress/zlib"
 	"encoding/base64"
 	"encoding/hex"
 	"fmt"
-	"github.com/rulego/streamsql/utils/cast"
-	"io"
 	"math"
 	"net/url"
 	"strconv"
 	"time"
+
+	"github.com/rulego/streamsql/utils/cast"
 )
 
 // CastFunction 类型转换函数
@@ -265,19 +262,19 @@ func (f *ConvertTzFunction) Execute(ctx *FunctionContext, args []interface{}) (i
 	default:
 		return nil, fmt.Errorf("time value must be time.Time or string")
 	}
-	
+
 	// 获取目标时区
 	timezone, err := cast.ToStringE(args[1])
 	if err != nil {
 		return nil, err
 	}
-	
+
 	// 加载时区
 	loc, err := time.LoadLocation(timezone)
 	if err != nil {
 		return nil, fmt.Errorf("invalid timezone: %s", timezone)
 	}
-	
+
 	// 转换时区
 	return t.In(loc), nil
 }
@@ -324,7 +321,7 @@ func (f *ToSecondsFunction) Execute(ctx *FunctionContext, args []interface{}) (i
 	default:
 		return nil, fmt.Errorf("time value must be time.Time or string")
 	}
-	
+
 	return t.Unix(), nil
 }
 
@@ -348,151 +345,115 @@ func (f *ChrFunction) Execute(ctx *FunctionContext, args []interface{}) (interfa
 	if err != nil {
 		return nil, err
 	}
-	
+
 	if code < 0 || code > 127 {
 		return nil, fmt.Errorf("ASCII code must be between 0 and 127, got %d", code)
 	}
-	
+
 	return string(rune(code)), nil
 }
 
+
+
+// UrlEncodeFunction URL编码函数
+type UrlEncodeFunction struct {
+	*BaseFunction
+}
+
+func NewUrlEncodeFunction() *UrlEncodeFunction {
+	return &UrlEncodeFunction{
+		BaseFunction: NewBaseFunction("url_encode", TypeConversion, "转换函数", "URL编码", 1, 1),
+	}
+}
+
+func (f *UrlEncodeFunction) Validate(args []interface{}) error {
+	return f.ValidateArgCount(args)
+}
+
+func (f *UrlEncodeFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
+	if err := f.Validate(args); err != nil {
+		return nil, err
+	}
+
+	if args[0] == nil {
+		return nil, fmt.Errorf("url_encode: input cannot be nil")
+	}
+
+	input := cast.ToString(args[0])
+	return url.QueryEscape(input), nil
+}
+
+// UrlDecodeFunction URL解码函数
+type UrlDecodeFunction struct {
+	*BaseFunction
+}
+
+func NewUrlDecodeFunction() *UrlDecodeFunction {
+	return &UrlDecodeFunction{
+		BaseFunction: NewBaseFunction("url_decode", TypeConversion, "转换函数", "URL解码", 1, 1),
+	}
+}
+
+func (f *UrlDecodeFunction) Validate(args []interface{}) error {
+	return f.ValidateArgCount(args)
+}
+
+func (f *UrlDecodeFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
+	if err := f.Validate(args); err != nil {
+		return nil, err
+	}
+
+	if args[0] == nil {
+		return nil, fmt.Errorf("url_decode: input cannot be nil")
+	}
+
+	input := cast.ToString(args[0])
+	result, err := url.QueryUnescape(input)
+	if err != nil {
+		return nil, fmt.Errorf("URL decode failed: %v", err)
+	}
+	return result, nil
+}
+
 // TruncFunction 截断小数位数
 type TruncFunction struct {
 	*BaseFunction
 }
 
+// NewTruncFunction 创建新的 trunc 函数
 func NewTruncFunction() *TruncFunction {
 	return &TruncFunction{
 		BaseFunction: NewBaseFunction("trunc", TypeConversion, "转换函数", "截断小数位数", 2, 2),
 	}
 }
 
+// Validate 验证参数
 func (f *TruncFunction) Validate(args []interface{}) error {
 	return f.ValidateArgCount(args)
 }
 
+// Execute 执行函数
 func (f *TruncFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
-	val, err := cast.ToFloat64E(args[0])
-	if err != nil {
+	if err := f.Validate(args); err != nil {
 		return nil, err
 	}
-	
-	precision, err := cast.ToIntE(args[1])
-	if err != nil {
-		return nil, err
-	}
-	
+
+	// 转换第一个参数为浮点数
+	num := cast.ToFloat64(args[0])
+
+	// 转换第二个参数为整数（精度）
+	precision := cast.ToInt(args[1])
+
+	// 精度不能为负数
 	if precision < 0 {
-		return nil, fmt.Errorf("precision must be non-negative, got %d", precision)
+		return nil, fmt.Errorf("trunc precision cannot be negative")
 	}
-	
+
 	// 计算截断
 	multiplier := math.Pow(10, float64(precision))
-	return math.Trunc(val*multiplier) / multiplier, nil
-}
-
-// CompressFunction 压缩函数
-type CompressFunction struct {
-	*BaseFunction
-}
-
-func NewCompressFunction() *CompressFunction {
-	return &CompressFunction{
-		BaseFunction: NewBaseFunction("compress", TypeConversion, "转换函数", "压缩字符串或二进制值", 2, 2),
+	if num >= 0 {
+		return math.Floor(num*multiplier) / multiplier, nil
+	} else {
+		return math.Ceil(num*multiplier) / multiplier, nil
 	}
 }
-
-func (f *CompressFunction) Validate(args []interface{}) error {
-	return f.ValidateArgCount(args)
-}
-
-func (f *CompressFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
-	if err := f.Validate(args); err != nil {
-		return nil, err
-	}
-	
-	input := cast.ToString(args[0])
-	algorithm := cast.ToString(args[1])
-	
-	var buf bytes.Buffer
-	var writer io.WriteCloser
-	
-	switch algorithm {
-	case "gzip":
-		writer = gzip.NewWriter(&buf)
-	case "zlib":
-		writer = zlib.NewWriter(&buf)
-	default:
-		return nil, fmt.Errorf("unsupported compression algorithm: %s", algorithm)
-	}
-	
-	_, err := writer.Write([]byte(input))
-	if err != nil {
-		return nil, fmt.Errorf("compression failed: %v", err)
-	}
-	
-	err = writer.Close()
-	if err != nil {
-		return nil, fmt.Errorf("compression failed: %v", err)
-	}
-	
-	// 返回base64编码的压缩数据
-	return base64.StdEncoding.EncodeToString(buf.Bytes()), nil
-}
-
-// DecompressFunction 解压缩函数
-type DecompressFunction struct {
-	*BaseFunction
-}
-
-func NewDecompressFunction() *DecompressFunction {
-	return &DecompressFunction{
-		BaseFunction: NewBaseFunction("decompress", TypeConversion, "转换函数", "解压缩字符串或二进制值", 2, 2),
-	}
-}
-
-func (f *DecompressFunction) Validate(args []interface{}) error {
-	return f.ValidateArgCount(args)
-}
-
-func (f *DecompressFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
-	if err := f.Validate(args); err != nil {
-		return nil, err
-	}
-	
-	input := cast.ToString(args[0])
-	algorithm := cast.ToString(args[1])
-	
-	// 解码base64数据
-	compressedData, err := base64.StdEncoding.DecodeString(input)
-	if err != nil {
-		return nil, fmt.Errorf("invalid base64 input: %v", err)
-	}
-	
-	buf := bytes.NewReader(compressedData)
-	var reader io.ReadCloser
-	
-	switch algorithm {
-	case "gzip":
-		reader, err = gzip.NewReader(buf)
-		if err != nil {
-			return nil, fmt.Errorf("gzip decompression failed: %v", err)
-		}
-	case "zlib":
-		reader, err = zlib.NewReader(buf)
-		if err != nil {
-			return nil, fmt.Errorf("zlib decompression failed: %v", err)
-		}
-	default:
-		return nil, fmt.Errorf("unsupported decompression algorithm: %s", algorithm)
-	}
-	
-	defer reader.Close()
-	
-	result, err := io.ReadAll(reader)
-	if err != nil {
-		return nil, fmt.Errorf("decompression failed: %v", err)
-	}
-	
-	return string(result), nil
-}
diff --git a/functions/functions_conversion_test.go b/functions/functions_conversion_test.go
index 865e3d9..b0a367b 100644
--- a/functions/functions_conversion_test.go
+++ b/functions/functions_conversion_test.go
@@ -39,7 +39,7 @@ func TestNewConversionFunctions(t *testing.T) {
 			args:     []interface{}{"invalid-time", "UTC"},
 			wantErr:  true,
 		},
-		
+
 		// to_seconds 函数测试
 		{
 			name:     "to_seconds with time.Time",
@@ -61,7 +61,7 @@ func TestNewConversionFunctions(t *testing.T) {
 			args:     []interface{}{"invalid-time"},
 			wantErr:  true,
 		},
-		
+
 		// chr 函数测试
 		{
 			name:     "chr valid ASCII code",
@@ -89,7 +89,7 @@ func TestNewConversionFunctions(t *testing.T) {
 			args:     []interface{}{128},
 			wantErr:  true,
 		},
-		
+
 		// trunc 函数测试
 		{
 			name:     "trunc positive number",
@@ -98,6 +98,70 @@ func TestNewConversionFunctions(t *testing.T) {
 			want:     3.14,
 			wantErr:  false,
 		},
+
+		// url_encode 函数测试
+		{
+			name:     "url_encode basic",
+			funcName: "url_encode",
+			args:     []interface{}{"hello world"},
+			want:     "hello+world",
+			wantErr:  false,
+		},
+		{
+			name:     "url_encode special chars",
+			funcName: "url_encode",
+			args:     []interface{}{"hello@world.com"},
+			want:     "hello%40world.com",
+			wantErr:  false,
+		},
+		{
+			name:     "url_encode empty",
+			funcName: "url_encode",
+			args:     []interface{}{""},
+			want:     "",
+			wantErr:  false,
+		},
+		{
+			name:     "url_encode nil",
+			funcName: "url_encode",
+			args:     []interface{}{nil},
+			wantErr:  true,
+		},
+
+		// url_decode 函数测试
+		{
+			name:     "url_decode basic",
+			funcName: "url_decode",
+			args:     []interface{}{"hello+world"},
+			want:     "hello world",
+			wantErr:  false,
+		},
+		{
+			name:     "url_decode special chars",
+			funcName: "url_decode",
+			args:     []interface{}{"hello%40world.com"},
+			want:     "hello@world.com",
+			wantErr:  false,
+		},
+		{
+			name:     "url_decode empty",
+			funcName: "url_decode",
+			args:     []interface{}{""},
+			want:     "",
+			wantErr:  false,
+		},
+		{
+			name:     "url_decode nil",
+			funcName: "url_decode",
+			args:     []interface{}{nil},
+			wantErr:  true,
+		},
+		{
+			name:     "url_decode invalid",
+			funcName: "url_decode",
+			args:     []interface{}{"hello%ZZ"},
+			wantErr:  true,
+		},
 		{
 			name:     "trunc negative number",
 			funcName: "trunc",
@@ -119,20 +183,20 @@ func TestNewConversionFunctions(t *testing.T) {
 			wantErr:  true,
 		},
 	}
-	
+
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			fn, exists := Get(tt.funcName)
 			if !exists {
 				t.Fatalf("Function %s not found", tt.funcName)
 			}
-			
+
 			result, err := fn.Execute(nil, tt.args)
 			if (err != nil) != tt.wantErr {
 				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
-			
+
 			if !tt.wantErr {
 				// 对于时间类型，需要特殊处理比较
 				if tt.funcName == "convert_tz" {
@@ -157,4 +221,4 @@ func TestNewConversionFunctions(t *testing.T) {
 			}
 		})
 	}
-}
\ No newline at end of file
+}
diff --git a/functions/functions_datetime.go b/functions/functions_datetime.go
index 1c79992..a269ead 100644
--- a/functions/functions_datetime.go
+++ b/functions/functions_datetime.go
@@ -479,6 +479,12 @@ func (f *YearFunction) Validate(args []interface{}) error {
 }
 
 func (f *YearFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
+	// 首先检查是否是 time.Time 类型
+	if t, ok := args[0].(time.Time); ok {
+		return float64(t.Year()), nil
+	}
+
+	// 如果不是 time.Time，尝试转换为字符串并解析
 	dateStr, err := cast.ToStringE(args[0])
 	if err != nil {
 		return nil, fmt.Errorf("invalid date: %v", err)
@@ -491,7 +497,7 @@ func (f *YearFunction) Execute(ctx *FunctionContext, args []interface{}) (interf
 		}
 	}
 
-	return t.Year(), nil
+	return float64(t.Year()), nil
 }
 
 // MonthFunction 提取月份函数
@@ -510,6 +516,12 @@ func (f *MonthFunction) Validate(args []interface{}) error {
 }
 
 func (f *MonthFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
+	// 首先检查是否是 time.Time 类型
+	if t, ok := args[0].(time.Time); ok {
+		return float64(t.Month()), nil
+	}
+
+	// 如果不是 time.Time，尝试转换为字符串并解析
 	dateStr, err := cast.ToStringE(args[0])
 	if err != nil {
 		return nil, fmt.Errorf("invalid date: %v", err)
@@ -522,7 +534,7 @@ func (f *MonthFunction) Execute(ctx *FunctionContext, args []interface{}) (inter
 		}
 	}
 
-	return int(t.Month()), nil
+	return float64(t.Month()), nil
 }
 
 // DayFunction 提取日期函数
diff --git a/functions/functions_datetime_test.go b/functions/functions_datetime_test.go
index 8e513d5..e78c345 100644
--- a/functions/functions_datetime_test.go
+++ b/functions/functions_datetime_test.go
@@ -63,7 +63,7 @@ func TestDateTimeFunctions(t *testing.T) {
 			name:     "year extraction",
 			function: NewYearFunction(),
 			args:     []interface{}{"2023-12-25 15:30:45"},
-			expected: 2023,
+			expected: float64(2023),
 			wantErr:  false,
 		},
 		// MonthFunction 测试
@@ -71,7 +71,7 @@ func TestDateTimeFunctions(t *testing.T) {
 			name:     "month extraction",
 			function: NewMonthFunction(),
 			args:     []interface{}{"2023-12-25 15:30:45"},
-			expected: 12,
+			expected: float64(12),
 			wantErr:  false,
 		},
 		// DayFunction 测试
@@ -164,14 +164,14 @@ func TestDateTimeFunctions(t *testing.T) {
 				}
 				return
 			}
-			
+
 			// 执行函数
 			result, err := tt.function.Execute(nil, tt.args)
 			if (err != nil) != tt.wantErr {
 				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
-			
+
 			if !tt.wantErr && result != tt.expected {
 				t.Errorf("Execute() = %v, want %v", result, tt.expected)
 			}
@@ -235,4 +235,4 @@ func TestDateFormatConversion(t *testing.T) {
 			}
 		})
 	}
-}
\ No newline at end of file
+}
diff --git a/functions/functions_hash.go b/functions/functions_hash.go
index a4bab70..3aee7c9 100644
--- a/functions/functions_hash.go
+++ b/functions/functions_hash.go
@@ -28,7 +28,7 @@ func (f *Md5Function) Execute(ctx *FunctionContext, args []interface{}) (interfa
 	if !ok {
 		return nil, fmt.Errorf("md5 requires string input")
 	}
-	
+
 	hash := md5.Sum([]byte(str))
 	return fmt.Sprintf("%x", hash), nil
 }
@@ -53,7 +53,7 @@ func (f *Sha1Function) Execute(ctx *FunctionContext, args []interface{}) (interf
 	if !ok {
 		return nil, fmt.Errorf("sha1 requires string input")
 	}
-	
+
 	hash := sha1.Sum([]byte(str))
 	return fmt.Sprintf("%x", hash), nil
 }
@@ -78,7 +78,7 @@ func (f *Sha256Function) Execute(ctx *FunctionContext, args []interface{}) (inte
 	if !ok {
 		return nil, fmt.Errorf("sha256 requires string input")
 	}
-	
+
 	hash := sha256.Sum256([]byte(str))
 	return fmt.Sprintf("%x", hash), nil
 }
@@ -103,7 +103,7 @@ func (f *Sha512Function) Execute(ctx *FunctionContext, args []interface{}) (inte
 	if !ok {
 		return nil, fmt.Errorf("sha512 requires string input")
 	}
-	
+
 	hash := sha512.Sum512([]byte(str))
 	return fmt.Sprintf("%x", hash), nil
-}
\ No newline at end of file
+}
diff --git a/functions/functions_hash_test.go b/functions/functions_hash_test.go
new file mode 100644
index 0000000..67bcc40
--- /dev/null
+++ b/functions/functions_hash_test.go
@@ -0,0 +1,53 @@
+package functions
+
+import (
+	"testing"
+)
+
+// 测试哈希函数
+func TestHashFunctions(t *testing.T) {
+	tests := []struct {
+		name     string
+		funcName string
+		args     []interface{}
+		expected interface{}
+	}{
+		{
+			name:     "md5 basic",
+			funcName: "md5",
+			args:     []interface{}{"hello"},
+			expected: "5d41402abc4b2a76b9719d911017c592",
+		},
+		{
+			name:     "sha1 basic",
+			funcName: "sha1",
+			args:     []interface{}{"hello"},
+			expected: "aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d",
+		},
+		{
+			name:     "sha256 basic",
+			funcName: "sha256",
+			args:     []interface{}{"hello"},
+			expected: "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fn, exists := Get(tt.funcName)
+			if !exists {
+				t.Fatalf("Function %s not found", tt.funcName)
+			}
+
+			result, err := fn.Execute(&FunctionContext{}, tt.args)
+			if err != nil {
+				t.Errorf("Execute() error = %v", err)
+				return
+			}
+
+			if result != tt.expected {
+				t.Errorf("Execute() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}
\ No newline at end of file
diff --git a/functions/functions_json.go b/functions/functions_json.go
index 10d39fc..35bfa05 100644
--- a/functions/functions_json.go
+++ b/functions/functions_json.go
@@ -50,7 +50,7 @@ func (f *FromJsonFunction) Execute(ctx *FunctionContext, args []interface{}) (in
 	if !ok {
 		return nil, fmt.Errorf("from_json requires string input")
 	}
-	
+
 	var result interface{}
 	err := json.Unmarshal([]byte(jsonStr), &result)
 	if err != nil {
@@ -79,18 +79,18 @@ func (f *JsonExtractFunction) Execute(ctx *FunctionContext, args []interface{})
 	if !ok {
 		return nil, fmt.Errorf("json_extract requires string input")
 	}
-	
+
 	path, ok := args[1].(string)
 	if !ok {
 		return nil, fmt.Errorf("json_extract path must be string")
 	}
-	
+
 	var data interface{}
 	err := json.Unmarshal([]byte(jsonStr), &data)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse JSON: %v", err)
 	}
-	
+
 	// 简单的路径提取，支持 $.field 格式
 	if strings.HasPrefix(path, "$.") {
 		field := path[2:]
@@ -98,7 +98,7 @@ func (f *JsonExtractFunction) Execute(ctx *FunctionContext, args []interface{})
 			return dataMap[field], nil
 		}
 	}
-	
+
 	return nil, fmt.Errorf("invalid JSON path or data structure")
 }
 
@@ -122,7 +122,7 @@ func (f *JsonValidFunction) Execute(ctx *FunctionContext, args []interface{}) (i
 	if !ok {
 		return false, nil
 	}
-	
+
 	var temp interface{}
 	err := json.Unmarshal([]byte(jsonStr), &temp)
 	return err == nil, nil
@@ -148,13 +148,13 @@ func (f *JsonTypeFunction) Execute(ctx *FunctionContext, args []interface{}) (in
 	if !ok {
 		return "unknown", nil
 	}
-	
+
 	var data interface{}
 	err := json.Unmarshal([]byte(jsonStr), &data)
 	if err != nil {
 		return "invalid", nil
 	}
-	
+
 	switch data.(type) {
 	case nil:
 		return "null", nil
@@ -193,13 +193,13 @@ func (f *JsonLengthFunction) Execute(ctx *FunctionContext, args []interface{}) (
 	if !ok {
 		return nil, fmt.Errorf("json_length requires string input")
 	}
-	
+
 	var data interface{}
 	err := json.Unmarshal([]byte(jsonStr), &data)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse JSON: %v", err)
 	}
-	
+
 	switch v := data.(type) {
 	case []interface{}:
 		return len(v), nil
@@ -208,4 +208,4 @@ func (f *JsonLengthFunction) Execute(ctx *FunctionContext, args []interface{}) (
 	default:
 		return nil, fmt.Errorf("JSON value is not an array or object")
 	}
-}
\ No newline at end of file
+}
diff --git a/functions/functions_json_test.go b/functions/functions_json_test.go
new file mode 100644
index 0000000..ee34c08
--- /dev/null
+++ b/functions/functions_json_test.go
@@ -0,0 +1,105 @@
+package functions
+
+import (
+	"testing"
+)
+
+// 测试JSON函数
+func TestJsonFunctions(t *testing.T) {
+	tests := []struct {
+		name     string
+		funcName string
+		args     []interface{}
+		expected interface{}
+		wantErr  bool
+	}{
+		{
+			name:     "to_json basic",
+			funcName: "to_json",
+			args:     []interface{}{map[string]interface{}{"name": "test", "value": 123}},
+			expected: `{"name":"test","value":123}`,
+		},
+		{
+			name:     "from_json basic",
+			funcName: "from_json",
+			args:     []interface{}{`{"name":"test","value":123}`},
+			expected: map[string]interface{}{"name": "test", "value": float64(123)},
+		},
+		{
+			name:     "json_extract basic",
+			funcName: "json_extract",
+			args:     []interface{}{`{"name":"test","value":123}`, "$.name"},
+			expected: "test",
+		},
+		{
+			name:     "json_valid true",
+			funcName: "json_valid",
+			args:     []interface{}{`{"name":"test"}`},
+			expected: true,
+		},
+		{
+			name:     "json_valid false",
+			funcName: "json_valid",
+			args:     []interface{}{`{"name":"test"`},
+			expected: false,
+		},
+		{
+			name:     "json_type object",
+			funcName: "json_type",
+			args:     []interface{}{`{"name":"test"}`},
+			expected: "object",
+		},
+		{
+			name:     "json_length array",
+			funcName: "json_length",
+			args:     []interface{}{`[1,2,3]`},
+			expected: 3,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fn, exists := Get(tt.funcName)
+			if !exists {
+				t.Fatalf("Function %s not found", tt.funcName)
+			}
+
+			result, err := fn.Execute(&FunctionContext{}, tt.args)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if !tt.wantErr && !compareResults(result, tt.expected) {
+				t.Errorf("Execute() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}
+
+// 辅助函数：比较结果
+func compareResults(a, b interface{}) bool {
+	if a == nil && b == nil {
+		return true
+	}
+	if a == nil || b == nil {
+		return false
+	}
+
+	// 对于map类型的特殊处理
+	if mapA, okA := a.(map[string]interface{}); okA {
+		if mapB, okB := b.(map[string]interface{}); okB {
+			if len(mapA) != len(mapB) {
+				return false
+			}
+			for k, v := range mapA {
+				if mapB[k] != v {
+					return false
+				}
+			}
+			return true
+		}
+	}
+
+	return a == b
+}
\ No newline at end of file
diff --git a/functions/functions_multirow.go b/functions/functions_multirow.go
new file mode 100644
index 0000000..fe323ae
--- /dev/null
+++ b/functions/functions_multirow.go
@@ -0,0 +1,109 @@
+package functions
+
+import (
+	"fmt"
+	"reflect"
+)
+
+// UnnestFunction 将数组展开为多行
+type UnnestFunction struct {
+	*BaseFunction
+}
+
+func NewUnnestFunction() *UnnestFunction {
+	return &UnnestFunction{
+		BaseFunction: NewBaseFunction("unnest", TypeString, "多行函数", "将数组展开为多行", 1, 1),
+	}
+}
+
+func (f *UnnestFunction) Validate(args []interface{}) error {
+	return f.ValidateArgCount(args)
+}
+
+func (f *UnnestFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
+	if err := f.Validate(args); err != nil {
+		return nil, err
+	}
+
+	array := args[0]
+	if array == nil {
+		return []interface{}{}, nil
+	}
+
+	// 使用反射检查是否为数组或切片
+	v := reflect.ValueOf(array)
+	if v.Kind() != reflect.Slice && v.Kind() != reflect.Array {
+		return nil, fmt.Errorf("unnest requires an array or slice, got %T", array)
+	}
+
+	// 转换为 []interface{}
+	result := make([]interface{}, v.Len())
+	for i := 0; i < v.Len(); i++ {
+		elem := v.Index(i).Interface()
+		
+		// 如果数组元素是对象（map），则展开为列
+		if elemMap, ok := elem.(map[string]interface{}); ok {
+			// 对于对象，我们返回一个特殊的结构来表示需要展开为列
+			result[i] = map[string]interface{}{
+				"__unnest_object__": true,
+				"__data__":          elemMap,
+			}
+		} else {
+			result[i] = elem
+		}
+	}
+
+	return result, nil
+}
+
+// UnnestResult 表示 unnest 函数的结果
+type UnnestResult struct {
+	Rows []map[string]interface{}
+}
+
+// IsUnnestResult 检查是否为 unnest 结果
+func IsUnnestResult(value interface{}) bool {
+	if slice, ok := value.([]interface{}); ok {
+		for _, item := range slice {
+			if itemMap, ok := item.(map[string]interface{}); ok {
+				if unnest, exists := itemMap["__unnest_object__"]; exists {
+					if unnestBool, ok := unnest.(bool); ok && unnestBool {
+						return true
+					}
+				}
+			}
+		}
+	}
+	return false
+}
+
+// ProcessUnnestResult 处理 unnest 结果，将其转换为多行
+func ProcessUnnestResult(value interface{}) []map[string]interface{} {
+	slice, ok := value.([]interface{})
+	if !ok {
+		return nil
+	}
+
+	var rows []map[string]interface{}
+	for _, item := range slice {
+		if itemMap, ok := item.(map[string]interface{}); ok {
+			if unnest, exists := itemMap["__unnest_object__"]; exists {
+				if unnestBool, ok := unnest.(bool); ok && unnestBool {
+					if data, exists := itemMap["__data__"]; exists {
+						if dataMap, ok := data.(map[string]interface{}); ok {
+							rows = append(rows, dataMap)
+						}
+					}
+					continue
+				}
+			}
+		}
+		// 对于非对象元素，创建一个包含单个值的行
+		row := map[string]interface{}{
+			"value": item,
+		}
+		rows = append(rows, row)
+	}
+
+	return rows
+}
\ No newline at end of file
diff --git a/functions/functions_multirow_test.go b/functions/functions_multirow_test.go
new file mode 100644
index 0000000..83f14b6
--- /dev/null
+++ b/functions/functions_multirow_test.go
@@ -0,0 +1,119 @@
+package functions
+
+import (
+	"reflect"
+	"testing"
+)
+
+// TestUnnestFunction 测试unnest函数
+func TestUnnestFunction(t *testing.T) {
+	tests := []struct {
+		name     string
+		funcName string
+		args     []interface{}
+		expected interface{}
+		wantErr  bool
+	}{
+		// unnest 函数测试
+		{
+			name:     "unnest array",
+			funcName: "unnest",
+			args:     []interface{}{[]interface{}{1, 2, 3}},
+			expected: []interface{}{1, 2, 3},
+		},
+		{
+			name:     "unnest empty array",
+			funcName: "unnest",
+			args:     []interface{}{[]interface{}{}},
+			expected: []interface{}{},
+		},
+		{
+			name:     "unnest nil",
+			funcName: "unnest",
+			args:     []interface{}{nil},
+			expected: []interface{}{},
+		},
+		{
+			name:     "unnest non-array",
+			funcName: "unnest",
+			args:     []interface{}{"not an array"},
+			expected: nil,
+			wantErr:  true,
+		},
+
+
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fn, exists := Get(tt.funcName)
+			if !exists {
+				t.Fatalf("Function %s not found", tt.funcName)
+			}
+
+			result, err := fn.Execute(&FunctionContext{}, tt.args)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if !tt.wantErr {
+				if !reflect.DeepEqual(result, tt.expected) {
+					t.Errorf("Execute() = %v, want %v", result, tt.expected)
+				}
+			}
+		})
+	}
+}
+
+// TestUnnestWithObjects 测试 unnest 函数处理对象数组
+func TestUnnestWithObjects(t *testing.T) {
+	fn, exists := Get("unnest")
+	if !exists {
+		t.Fatal("Function unnest not found")
+	}
+
+	// 测试对象数组
+	objectArray := []interface{}{
+		map[string]interface{}{"name": "Alice", "age": 30},
+		map[string]interface{}{"name": "Bob", "age": 25},
+	}
+
+	result, err := fn.Execute(&FunctionContext{}, []interface{}{objectArray})
+	if err != nil {
+		t.Fatalf("Execute() error = %v", err)
+	}
+
+	// 检查结果是否包含特殊标记
+	resultSlice, ok := result.([]interface{})
+	if !ok {
+		t.Fatalf("Expected []interface{}, got %T", result)
+	}
+
+	if len(resultSlice) != 2 {
+		t.Fatalf("Expected 2 items, got %d", len(resultSlice))
+	}
+
+	// 检查第一个对象是否有特殊标记
+	firstItem, ok := resultSlice[0].(map[string]interface{})
+	if !ok {
+		t.Fatalf("Expected map[string]interface{}, got %T", resultSlice[0])
+	}
+
+	if unnestFlag, exists := firstItem["__unnest_object__"]; !exists || unnestFlag != true {
+		t.Error("Expected __unnest_object__ flag to be true")
+	}
+
+	if data, exists := firstItem["__data__"]; !exists {
+		t.Error("Expected __data__ field to exist")
+	} else {
+		dataMap, ok := data.(map[string]interface{})
+		if !ok {
+			t.Errorf("Expected __data__ to be map[string]interface{}, got %T", data)
+		} else {
+			if dataMap["name"] != "Alice" || dataMap["age"] != 30 {
+				t.Errorf("Unexpected data: %v", dataMap)
+			}
+		}
+	}
+}
\ No newline at end of file
diff --git a/functions/functions_new_test.go b/functions/functions_new_test.go
deleted file mode 100644
index c774c49..0000000
--- a/functions/functions_new_test.go
+++ /dev/null
@@ -1,339 +0,0 @@
-package functions
-
-import (
-	"testing"
-)
-
-// 测试JSON函数
-func TestJsonFunctions(t *testing.T) {
-	tests := []struct {
-		name     string
-		funcName string
-		args     []interface{}
-		expected interface{}
-		wantErr  bool
-	}{
-		{
-			name:     "to_json basic",
-			funcName: "to_json",
-			args:     []interface{}{map[string]interface{}{"name": "test", "value": 123}},
-			expected: `{"name":"test","value":123}`,
-		},
-		{
-			name:     "from_json basic",
-			funcName: "from_json",
-			args:     []interface{}{`{"name":"test","value":123}`},
-			expected: map[string]interface{}{"name": "test", "value": float64(123)},
-		},
-		{
-			name:     "json_extract basic",
-			funcName: "json_extract",
-			args:     []interface{}{`{"name":"test","value":123}`, "$.name"},
-			expected: "test",
-		},
-		{
-			name:     "json_valid true",
-			funcName: "json_valid",
-			args:     []interface{}{`{"name":"test"}`},
-			expected: true,
-		},
-		{
-			name:     "json_valid false",
-			funcName: "json_valid",
-			args:     []interface{}{`{"name":"test"`},
-			expected: false,
-		},
-		{
-			name:     "json_type object",
-			funcName: "json_type",
-			args:     []interface{}{`{"name":"test"}`},
-			expected: "object",
-		},
-		{
-			name:     "json_length array",
-			funcName: "json_length",
-			args:     []interface{}{`[1,2,3]`},
-			expected: 3,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			fn, exists := Get(tt.funcName)
-			if !exists {
-				t.Fatalf("Function %s not found", tt.funcName)
-			}
-
-			result, err := fn.Execute(&FunctionContext{}, tt.args)
-			if (err != nil) != tt.wantErr {
-				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
-				return
-			}
-
-			if !tt.wantErr && !compareResults(result, tt.expected) {
-				t.Errorf("Execute() = %v, want %v", result, tt.expected)
-			}
-		})
-	}
-}
-
-// 测试哈希函数
-func TestHashFunctions(t *testing.T) {
-	tests := []struct {
-		name     string
-		funcName string
-		args     []interface{}
-		expected interface{}
-	}{
-		{
-			name:     "md5 basic",
-			funcName: "md5",
-			args:     []interface{}{"hello"},
-			expected: "5d41402abc4b2a76b9719d911017c592",
-		},
-		{
-			name:     "sha1 basic",
-			funcName: "sha1",
-			args:     []interface{}{"hello"},
-			expected: "aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d",
-		},
-		{
-			name:     "sha256 basic",
-			funcName: "sha256",
-			args:     []interface{}{"hello"},
-			expected: "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			fn, exists := Get(tt.funcName)
-			if !exists {
-				t.Fatalf("Function %s not found", tt.funcName)
-			}
-
-			result, err := fn.Execute(&FunctionContext{}, tt.args)
-			if err != nil {
-				t.Errorf("Execute() error = %v", err)
-				return
-			}
-
-			if result != tt.expected {
-				t.Errorf("Execute() = %v, want %v", result, tt.expected)
-			}
-		})
-	}
-}
-
-// 测试数组函数
-func TestArrayFunctions(t *testing.T) {
-	tests := []struct {
-		name     string
-		funcName string
-		args     []interface{}
-		expected interface{}
-	}{
-		{
-			name:     "array_length basic",
-			funcName: "array_length",
-			args:     []interface{}{[]interface{}{1, 2, 3}},
-			expected: 3,
-		},
-		{
-			name:     "array_contains true",
-			funcName: "array_contains",
-			args:     []interface{}{[]interface{}{1, 2, 3}, 2},
-			expected: true,
-		},
-		{
-			name:     "array_contains false",
-			funcName: "array_contains",
-			args:     []interface{}{[]interface{}{1, 2, 3}, 4},
-			expected: false,
-		},
-		{
-			name:     "array_position found",
-			funcName: "array_position",
-			args:     []interface{}{[]interface{}{1, 2, 3}, 2},
-			expected: 2,
-		},
-		{
-			name:     "array_position not found",
-			funcName: "array_position",
-			args:     []interface{}{[]interface{}{1, 2, 3}, 4},
-			expected: 0,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			fn, exists := Get(tt.funcName)
-			if !exists {
-				t.Fatalf("Function %s not found", tt.funcName)
-			}
-
-			result, err := fn.Execute(&FunctionContext{}, tt.args)
-			if err != nil {
-				t.Errorf("Execute() error = %v", err)
-				return
-			}
-
-			if result != tt.expected {
-				t.Errorf("Execute() = %v, want %v", result, tt.expected)
-			}
-		})
-	}
-}
-
-// 测试类型检查函数
-func TestTypeFunctions(t *testing.T) {
-	tests := []struct {
-		name     string
-		funcName string
-		args     []interface{}
-		expected interface{}
-	}{
-		{
-			name:     "is_null true",
-			funcName: "is_null",
-			args:     []interface{}{nil},
-			expected: true,
-		},
-		{
-			name:     "is_null false",
-			funcName: "is_null",
-			args:     []interface{}{"test"},
-			expected: false,
-		},
-		{
-			name:     "is_numeric true",
-			funcName: "is_numeric",
-			args:     []interface{}{123},
-			expected: true,
-		},
-		{
-			name:     "is_numeric false",
-			funcName: "is_numeric",
-			args:     []interface{}{"test"},
-			expected: false,
-		},
-		{
-			name:     "is_string true",
-			funcName: "is_string",
-			args:     []interface{}{"test"},
-			expected: true,
-		},
-		{
-			name:     "is_string false",
-			funcName: "is_string",
-			args:     []interface{}{123},
-			expected: false,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			fn, exists := Get(tt.funcName)
-			if !exists {
-				t.Fatalf("Function %s not found", tt.funcName)
-			}
-
-			result, err := fn.Execute(&FunctionContext{}, tt.args)
-			if err != nil {
-				t.Errorf("Execute() error = %v", err)
-				return
-			}
-
-			if result != tt.expected {
-				t.Errorf("Execute() = %v, want %v", result, tt.expected)
-			}
-		})
-	}
-}
-
-// 测试条件函数
-func TestConditionalFunctions(t *testing.T) {
-	tests := []struct {
-		name     string
-		funcName string
-		args     []interface{}
-		expected interface{}
-	}{
-		{
-			name:     "coalesce first non-null",
-			funcName: "coalesce",
-			args:     []interface{}{nil, "test", "other"},
-			expected: "test",
-		},
-		{
-			name:     "nullif equal",
-			funcName: "nullif",
-			args:     []interface{}{"test", "test"},
-			expected: nil,
-		},
-		{
-			name:     "nullif not equal",
-			funcName: "nullif",
-			args:     []interface{}{"test", "other"},
-			expected: "test",
-		},
-		{
-			name:     "greatest numeric",
-			funcName: "greatest",
-			args:     []interface{}{1, 3, 2},
-			expected: 3,
-		},
-		{
-			name:     "least numeric",
-			funcName: "least",
-			args:     []interface{}{3, 1, 2},
-			expected: 1,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			fn, exists := Get(tt.funcName)
-			if !exists {
-				t.Fatalf("Function %s not found", tt.funcName)
-			}
-
-			result, err := fn.Execute(&FunctionContext{}, tt.args)
-			if err != nil {
-				t.Errorf("Execute() error = %v", err)
-				return
-			}
-
-			if !compareResults(result, tt.expected) {
-				t.Errorf("Execute() = %v, want %v", result, tt.expected)
-			}
-		})
-	}
-}
-
-// 辅助函数：比较结果
-func compareResults(a, b interface{}) bool {
-	if a == nil && b == nil {
-		return true
-	}
-	if a == nil || b == nil {
-		return false
-	}
-	
-	// 对于map类型的特殊处理
-	if mapA, okA := a.(map[string]interface{}); okA {
-		if mapB, okB := b.(map[string]interface{}); okB {
-			if len(mapA) != len(mapB) {
-				return false
-			}
-			for k, v := range mapA {
-				if mapB[k] != v {
-					return false
-				}
-			}
-			return true
-		}
-	}
-	
-	return a == b
-}
\ No newline at end of file
diff --git a/functions/functions_string.go b/functions/functions_string.go
index 4ba1353..4a55f03 100644
--- a/functions/functions_string.go
+++ b/functions/functions_string.go
@@ -2,9 +2,10 @@ package functions
 
 import (
 	"fmt"
-	"github.com/rulego/streamsql/utils/cast"
 	"regexp"
 	"strings"
+
+	"github.com/rulego/streamsql/utils/cast"
 )
 
 // ConcatFunction 字符串连接函数
@@ -292,26 +293,26 @@ func (f *SubstringFunction) Execute(ctx *FunctionContext, args []interface{}) (i
 	if err != nil {
 		return nil, err
 	}
-	
+
 	strLen := int64(len(str))
 	if start < 0 || start >= strLen {
 		return "", nil
 	}
-	
+
 	if len(args) == 2 {
 		return str[start:], nil
 	}
-	
+
 	length, err := cast.ToInt64E(args[2])
 	if err != nil {
 		return nil, err
 	}
-	
+
 	end := start + length
 	if end > strLen {
 		end = strLen
 	}
-	
+
 	return str[start:end], nil
 }
 
@@ -397,7 +398,7 @@ func (f *LpadFunction) Execute(ctx *FunctionContext, args []interface{}) (interf
 	if err != nil {
 		return nil, err
 	}
-	
+
 	pad := " "
 	if len(args) == 3 {
 		pad, err = cast.ToStringE(args[2])
@@ -405,12 +406,12 @@ func (f *LpadFunction) Execute(ctx *FunctionContext, args []interface{}) (interf
 			return nil, err
 		}
 	}
-	
+
 	strLen := int64(len(str))
 	if strLen >= length {
 		return str, nil
 	}
-	
+
 	padLen := length - strLen
 	padStr := strings.Repeat(pad, int(padLen/int64(len(pad))+1))
 	return padStr[:padLen] + str, nil
@@ -440,7 +441,7 @@ func (f *RpadFunction) Execute(ctx *FunctionContext, args []interface{}) (interf
 	if err != nil {
 		return nil, err
 	}
-	
+
 	pad := " "
 	if len(args) == 3 {
 		pad, err = cast.ToStringE(args[2])
@@ -448,12 +449,12 @@ func (f *RpadFunction) Execute(ctx *FunctionContext, args []interface{}) (interf
 			return nil, err
 		}
 	}
-	
+
 	strLen := int64(len(str))
 	if strLen >= length {
 		return str, nil
 	}
-	
+
 	padLen := length - strLen
 	padStr := strings.Repeat(pad, int(padLen/int64(len(pad))+1))
 	return str + padStr[:padLen], nil
@@ -533,7 +534,7 @@ func (f *RegexpMatchesFunction) Execute(ctx *FunctionContext, args []interface{}
 	if err != nil {
 		return nil, err
 	}
-	
+
 	matched, err := regexp.MatchString(pattern, str)
 	if err != nil {
 		return nil, err
@@ -569,7 +570,7 @@ func (f *RegexpReplaceFunction) Execute(ctx *FunctionContext, args []interface{}
 	if err != nil {
 		return nil, err
 	}
-	
+
 	re, err := regexp.Compile(pattern)
 	if err != nil {
 		return nil, err
@@ -601,12 +602,12 @@ func (f *RegexpSubstringFunction) Execute(ctx *FunctionContext, args []interface
 	if err != nil {
 		return nil, err
 	}
-	
+
 	re, err := regexp.Compile(pattern)
 	if err != nil {
 		return nil, err
 	}
-	
+
 	match := re.FindString(str)
 	return match, nil
 }
diff --git a/functions/functions_string_test.go b/functions/functions_string_test.go
index a846a18..55859a4 100644
--- a/functions/functions_string_test.go
+++ b/functions/functions_string_test.go
@@ -16,88 +16,88 @@ func TestNewStringFunctions(t *testing.T) {
 		{"endswith_true", "endswith", []interface{}{"hello world", "world"}, true, false},
 		{"endswith_false", "endswith", []interface{}{"hello world", "hello"}, false, false},
 		{"endswith_empty", "endswith", []interface{}{"hello", ""}, true, false},
-		
+
 		// startswith tests
 		{"startswith_true", "startswith", []interface{}{"hello world", "hello"}, true, false},
 		{"startswith_false", "startswith", []interface{}{"hello world", "world"}, false, false},
 		{"startswith_empty", "startswith", []interface{}{"hello", ""}, true, false},
-		
+
 		// indexof tests
 		{"indexof_found", "indexof", []interface{}{"hello world", "world"}, int64(6), false},
 		{"indexof_not_found", "indexof", []interface{}{"hello world", "xyz"}, int64(-1), false},
 		{"indexof_first_char", "indexof", []interface{}{"hello", "h"}, int64(0), false},
-		
+
 		// substring tests
 		{"substring_start_only", "substring", []interface{}{"hello world", int64(6)}, "world", false},
 		{"substring_start_length", "substring", []interface{}{"hello world", int64(0), int64(5)}, "hello", false},
 		{"substring_out_of_bounds", "substring", []interface{}{"hello", int64(10)}, "", false},
-		
+
 		// replace tests
 		{"replace_simple", "replace", []interface{}{"hello world", "world", "Go"}, "hello Go", false},
 		{"replace_multiple", "replace", []interface{}{"hello hello", "hello", "hi"}, "hi hi", false},
 		{"replace_not_found", "replace", []interface{}{"hello world", "xyz", "abc"}, "hello world", false},
-		
+
 		// split tests
 		{"split_comma", "split", []interface{}{"a,b,c", ","}, []string{"a", "b", "c"}, false},
 		{"split_space", "split", []interface{}{"hello world", " "}, []string{"hello", "world"}, false},
 		{"split_not_found", "split", []interface{}{"hello", ","}, []string{"hello"}, false},
-		
+
 		// lpad tests
 		{"lpad_default", "lpad", []interface{}{"hello", int64(10)}, "     hello", false},
 		{"lpad_custom", "lpad", []interface{}{"hello", int64(8), "*"}, "***hello", false},
 		{"lpad_no_padding", "lpad", []interface{}{"hello", int64(3)}, "hello", false},
-		
+
 		// rpad tests
 		{"rpad_default", "rpad", []interface{}{"hello", int64(10)}, "hello     ", false},
 		{"rpad_custom", "rpad", []interface{}{"hello", int64(8), "*"}, "hello***", false},
 		{"rpad_no_padding", "rpad", []interface{}{"hello", int64(3)}, "hello", false},
-		
+
 		// ltrim tests
 		{"ltrim_spaces", "ltrim", []interface{}{"   hello world   "}, "hello world   ", false},
 		{"ltrim_tabs", "ltrim", []interface{}{"\t\nhello"}, "hello", false},
 		{"ltrim_no_whitespace", "ltrim", []interface{}{"hello"}, "hello", false},
-		
+
 		// rtrim tests
 		{"rtrim_spaces", "rtrim", []interface{}{"   hello world   "}, "   hello world", false},
 		{"rtrim_tabs", "rtrim", []interface{}{"hello\t\n"}, "hello", false},
 		{"rtrim_no_whitespace", "rtrim", []interface{}{"hello"}, "hello", false},
-		
+
 		// regexp_matches tests
 		{"regexp_matches_true", "regexp_matches", []interface{}{"hello123", "[0-9]+"}, true, false},
 		{"regexp_matches_false", "regexp_matches", []interface{}{"hello", "[0-9]+"}, false, false},
 		{"regexp_matches_email", "regexp_matches", []interface{}{"test@example.com", "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$"}, true, false},
-		
+
 		// regexp_replace tests
 		{"regexp_replace_digits", "regexp_replace", []interface{}{"hello123world456", "[0-9]+", "X"}, "helloXworldX", false},
 		{"regexp_replace_no_match", "regexp_replace", []interface{}{"hello", "[0-9]+", "X"}, "hello", false},
-		
+
 		// regexp_substring tests
 		{"regexp_substring_found", "regexp_substring", []interface{}{"hello123world", "[0-9]+"}, "123", false},
 		{"regexp_substring_not_found", "regexp_substring", []interface{}{"hello", "[0-9]+"}, "", false},
 	}
-	
+
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			fn, exists := Get(tt.funcName)
 			if !exists {
 				t.Fatalf("Function %s not found", tt.funcName)
 			}
-			
+
 			ctx := &FunctionContext{}
 			result, err := fn.Execute(ctx, tt.args)
-			
+
 			if tt.wantErr {
 				if err == nil {
 					t.Errorf("Expected error for %s, got nil", tt.name)
 				}
 				return
 			}
-			
+
 			if err != nil {
 				t.Errorf("Unexpected error for %s: %v", tt.name, err)
 				return
 			}
-			
+
 			// 特殊处理 split 函数的结果比较
 			if tt.funcName == "split" {
 				expectedSlice, ok := tt.expected.([]string)
@@ -127,4 +127,4 @@ func TestNewStringFunctions(t *testing.T) {
 			}
 		})
 	}
-}
\ No newline at end of file
+}
diff --git a/functions/functions_type.go b/functions/functions_type.go
index f1cd2c9..d9a6cb9 100644
--- a/functions/functions_type.go
+++ b/functions/functions_type.go
@@ -61,7 +61,7 @@ func (f *IsNumericFunction) Execute(ctx *FunctionContext, args []interface{}) (i
 	if args[0] == nil {
 		return false, nil
 	}
-	
+
 	v := reflect.ValueOf(args[0])
 	switch v.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
@@ -92,7 +92,7 @@ func (f *IsStringFunction) Execute(ctx *FunctionContext, args []interface{}) (in
 	if args[0] == nil {
 		return false, nil
 	}
-	
+
 	_, ok := args[0].(string)
 	return ok, nil
 }
@@ -116,7 +116,7 @@ func (f *IsBoolFunction) Execute(ctx *FunctionContext, args []interface{}) (inte
 	if args[0] == nil {
 		return false, nil
 	}
-	
+
 	_, ok := args[0].(bool)
 	return ok, nil
 }
@@ -140,7 +140,7 @@ func (f *IsArrayFunction) Execute(ctx *FunctionContext, args []interface{}) (int
 	if args[0] == nil {
 		return false, nil
 	}
-	
+
 	v := reflect.ValueOf(args[0])
 	return v.Kind() == reflect.Slice || v.Kind() == reflect.Array, nil
 }
@@ -164,7 +164,7 @@ func (f *IsObjectFunction) Execute(ctx *FunctionContext, args []interface{}) (in
 	if args[0] == nil {
 		return false, nil
 	}
-	
+
 	v := reflect.ValueOf(args[0])
 	return v.Kind() == reflect.Map || v.Kind() == reflect.Struct, nil
-}
\ No newline at end of file
+}
diff --git a/functions/functions_type_test.go b/functions/functions_type_test.go
new file mode 100644
index 0000000..31f0b04
--- /dev/null
+++ b/functions/functions_type_test.go
@@ -0,0 +1,95 @@
+package functions
+
+import (
+	"testing"
+)
+
+// 测试类型检查函数
+func TestTypeFunctions(t *testing.T) {
+	tests := []struct {
+		name     string
+		funcName string
+		args     []interface{}
+		expected interface{}
+	}{
+		{
+			name:     "is_null true",
+			funcName: "is_null",
+			args:     []interface{}{nil},
+			expected: true,
+		},
+		{
+			name:     "is_null false",
+			funcName: "is_null",
+			args:     []interface{}{"test"},
+			expected: false,
+		},
+		{
+			name:     "is_not_null true",
+			funcName: "is_not_null",
+			args:     []interface{}{"test"},
+			expected: true,
+		},
+		{
+			name:     "is_not_null false",
+			funcName: "is_not_null",
+			args:     []interface{}{nil},
+			expected: false,
+		},
+		{
+			name:     "is_numeric true",
+			funcName: "is_numeric",
+			args:     []interface{}{123},
+			expected: true,
+		},
+		{
+			name:     "is_numeric false",
+			funcName: "is_numeric",
+			args:     []interface{}{"test"},
+			expected: false,
+		},
+		{
+			name:     "is_string true",
+			funcName: "is_string",
+			args:     []interface{}{"test"},
+			expected: true,
+		},
+		{
+			name:     "is_string false",
+			funcName: "is_string",
+			args:     []interface{}{123},
+			expected: false,
+		},
+		{
+			name:     "is_bool true",
+			funcName: "is_bool",
+			args:     []interface{}{true},
+			expected: true,
+		},
+		{
+			name:     "is_bool false",
+			funcName: "is_bool",
+			args:     []interface{}{"test"},
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fn, exists := Get(tt.funcName)
+			if !exists {
+				t.Fatalf("Function %s not found", tt.funcName)
+			}
+
+			result, err := fn.Execute(&FunctionContext{}, tt.args)
+			if err != nil {
+				t.Errorf("Execute() error = %v", err)
+				return
+			}
+
+			if result != tt.expected {
+				t.Errorf("Execute() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}
\ No newline at end of file
diff --git a/functions/functions_window.go b/functions/functions_window.go
index c2067b5..c87b067 100644
--- a/functions/functions_window.go
+++ b/functions/functions_window.go
@@ -303,34 +303,69 @@ func (f *FirstValueFunction) Clone() AggregatorFunction {
 // LeadFunction 返回当前行之后第N行的值
 type LeadFunction struct {
 	*BaseFunction
-	values []interface{}
+	values       []interface{}
+	offset       int
+	defaultValue interface{}
+	hasDefault   bool
 }
 
 func NewLeadFunction() *LeadFunction {
 	return &LeadFunction{
 		BaseFunction: NewBaseFunction("lead", TypeWindow, "窗口函数", "返回当前行之后第N行的值", 1, 3),
 		values:       make([]interface{}, 0),
+		offset:       1, // 默认偏移量为1
 	}
 }
 
 func (f *LeadFunction) Validate(args []interface{}) error {
-	return f.ValidateArgCount(args)
+	if err := f.ValidateArgCount(args); err != nil {
+		return err
+	}
+
+	// 验证第二个参数（offset）是否为整数
+	if len(args) >= 2 {
+		if offset, ok := args[1].(int); ok {
+			f.offset = offset
+		} else {
+			return fmt.Errorf("offset must be an integer")
+		}
+	}
+
+	// 设置默认值
+	if len(args) >= 3 {
+		f.defaultValue = args[2]
+		f.hasDefault = true
+	}
+
+	return nil
 }
 
 func (f *LeadFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	if err := f.Validate(args); err != nil {
 		return nil, err
 	}
-	
-	// 获取默认值
-	var defaultValue interface{}
-	if len(args) >= 3 {
-		defaultValue = args[2]
+
+	// 获取偏移量
+	if len(args) >= 2 {
+		if offset, ok := args[1].(int); ok {
+			f.offset = offset
+		} else {
+			return nil, fmt.Errorf("offset must be an integer")
+		}
 	}
-	
+
+	// 获取默认值
+	if len(args) >= 3 {
+		f.defaultValue = args[2]
+		f.hasDefault = true
+	}
+
 	// Lead函数需要在窗口处理完成后才能确定值
 	// 这里返回默认值，实际实现需要在窗口引擎中处理
-	return defaultValue, nil
+	if f.hasDefault {
+		return f.defaultValue, nil
+	}
+	return nil, nil
 }
 
 // 实现AggregatorFunction接口
@@ -338,6 +373,9 @@ func (f *LeadFunction) New() AggregatorFunction {
 	return &LeadFunction{
 		BaseFunction: f.BaseFunction,
 		values:       make([]interface{}, 0),
+		offset:       f.offset,
+		defaultValue: f.defaultValue,
+		hasDefault:   f.hasDefault,
 	}
 }
 
@@ -347,18 +385,28 @@ func (f *LeadFunction) Add(value interface{}) {
 
 func (f *LeadFunction) Result() interface{} {
 	// Lead函数的结果需要在所有数据添加完成后计算
+	// 如果没有足够的数据，返回默认值
+	if len(f.values) == 0 && f.hasDefault {
+		return f.defaultValue
+	}
 	// 这里简化实现，返回nil
 	return nil
 }
 
 func (f *LeadFunction) Reset() {
 	f.values = make([]interface{}, 0)
+	f.offset = 1
+	f.defaultValue = nil
+	f.hasDefault = false
 }
 
 func (f *LeadFunction) Clone() AggregatorFunction {
 	clone := &LeadFunction{
 		BaseFunction: f.BaseFunction,
 		values:       make([]interface{}, len(f.values)),
+		offset:       f.offset,
+		defaultValue: f.defaultValue,
+		hasDefault:   f.hasDefault,
 	}
 	copy(clone.values, f.values)
 	return clone
@@ -380,14 +428,35 @@ func NewNthValueFunction() *NthValueFunction {
 }
 
 func (f *NthValueFunction) Validate(args []interface{}) error {
-	return f.ValidateArgCount(args)
+	if err := f.ValidateArgCount(args); err != nil {
+		return err
+	}
+	
+	// 验证N值
+	n := 1
+	if nVal, ok := args[1].(int); ok {
+		n = nVal
+	} else if nVal, ok := args[1].(int64); ok {
+		n = int(nVal)
+	} else {
+		return fmt.Errorf("nth_value n must be an integer")
+	}
+	
+	if n <= 0 {
+		return fmt.Errorf("nth_value n must be positive, got %d", n)
+	}
+	
+	// 设置n值
+	f.n = n
+	
+	return nil
 }
 
 func (f *NthValueFunction) Execute(ctx *FunctionContext, args []interface{}) (interface{}, error) {
 	if err := f.Validate(args); err != nil {
 		return nil, err
 	}
-	
+
 	// 获取N值
 	n := 1
 	if nVal, ok := args[1].(int); ok {
@@ -397,16 +466,16 @@ func (f *NthValueFunction) Execute(ctx *FunctionContext, args []interface{}) (in
 	} else {
 		return nil, fmt.Errorf("nth_value n must be an integer")
 	}
-	
+
 	if n <= 0 {
 		return nil, fmt.Errorf("nth_value n must be positive, got %d", n)
 	}
-	
+
 	// 返回第N个值（1-based索引）
 	if len(f.values) >= n {
 		return f.values[n-1], nil
 	}
-	
+
 	return nil, nil
 }
 
diff --git a/functions/functions_window_test.go b/functions/functions_window_test.go
index 531c32a..451e2e9 100644
--- a/functions/functions_window_test.go
+++ b/functions/functions_window_test.go
@@ -4,6 +4,20 @@ import (
 	"testing"
 )
 
+// isWindowFunction 判断是否为窗口函数
+func isWindowFunction(funcName string) bool {
+	windowFunctions := map[string]bool{
+		"row_number":   true,
+		"window_start": true,
+		"window_end":   true,
+		"lead":         true,
+		"lag":          true,
+		"first_value":  true,
+		"last_value":   true,
+	}
+	return windowFunctions[funcName]
+}
+
 func TestNewWindowFunctions(t *testing.T) {
 	tests := []struct {
 		name     string
@@ -222,8 +236,19 @@ func TestNewWindowFunctions(t *testing.T) {
 				tt.setup(aggInstance)
 			}
 			
-			// 执行函数
-			_, err = fn.Execute(nil, tt.args)
+			// 对于窗口函数测试，不需要调用Execute方法
+			// Execute方法主要用于流式处理，这里我们直接测试聚合器的Result方法
+			// 如果需要测试Execute方法，应该在原始函数实例上调用
+			if !isWindowFunction(tt.funcName) {
+				// 对于非窗口函数，在聚合器实例上执行
+				if aggFunc, ok := aggInstance.(Function); ok {
+					_, err = aggFunc.Execute(nil, tt.args)
+				} else {
+					// 执行函数
+					_, err = fn.Execute(nil, tt.args)
+				}
+			}
+			
 			if (err != nil) != tt.wantErr {
 				t.Errorf("Execute() error = %v, wantErr %v", err, tt.wantErr)
 				return
@@ -249,6 +274,11 @@ func TestWindowFunctionBasics(t *testing.T) {
 			t.Fatal("row_number function not found")
 		}
 		
+		// 重置函数状态
+		if rowNum, ok := rowNumFunc.(*RowNumberFunction); ok {
+			rowNum.Reset()
+		}
+		
 		// 测试行号递增
 		result1, err := rowNumFunc.Execute(nil, []interface{}{})
 		if err != nil {