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[ci skip] Consolidate docs for find

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Put all options for overloading `find` in one section
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schneems 2014-06-28 14:38:16 -05:00
parent d4fd0bd177
commit 63f4155596
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guides/source/active_record_querying.md
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@ -93,9 +93,9 @@ The primary operation of `Model.find(options)` can be summarized as:
Active Record provides several different ways of retrieving a single object.
#### Using a Primary Key
#### `find`
Using `Model.find(primary_key)`, you can retrieve the object corresponding to the specified _primary key_ that matches any supplied options. For example:
Using the `find` method, you can retrieve the object corresponding to the specified _primary key_ that matches any supplied options. For example:
```ruby
# Find the client with primary key (id) 10.
@ -109,7 +109,23 @@ The SQL equivalent of the above is:
SELECT * FROM clients WHERE (clients.id = 10) LIMIT 1
```
`Model.find(primary_key)` will raise an `ActiveRecord::RecordNotFound` exception if no matching record is found.
The `find` method will raise an `ActiveRecord::RecordNotFound` exception if no matching record is found.
You can also use this method to query for multiple objects. Call the `find` method and pass in an array of primary keys. The return will be an array containing all of the matching records for the supplied _primary keys_. For example:
```ruby
# Find the clients with primary keys 1 and 10.
client = Client.find([1, 10]) # Or even Client.find(1, 10)
# => [#<Client id: 1, first_name: "Lifo">, #<Client id: 10, first_name: "Ryan">]
```
The SQL equivalent of the above is:
```sql
SELECT * FROM clients WHERE (clients.id IN (1,10))
```
WARNING: The `find` method will raise an `ActiveRecord::RecordNotFound` exception unless a matching record is found for **all** of the supplied primary keys.
#### `take`
@ -268,28 +284,6 @@ SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1
`Model.last!` raises `ActiveRecord::RecordNotFound` if no matching record is found.
### Retrieving Multiple Objects
#### Using Multiple Primary Keys
`Model.find(array_of_primary_key)` accepts an array of _primary keys_, returning an array containing all of the matching records for the supplied _primary keys_. For example:
```ruby
# Find the clients with primary keys 1 and 10.
client = Client.find([1, 10]) # Or even Client.find(1, 10)
# => [#<Client id: 1, first_name: "Lifo">, #<Client id: 10, first_name: "Ryan">]
```
The SQL equivalent of the above is:
```sql
SELECT * FROM clients WHERE (clients.id IN (1,10))
```
WARNING: `Model.find(array_of_primary_key)` will raise an `ActiveRecord::RecordNotFound` exception unless a matching record is found for **all** of the supplied primary keys.
### Retrieving Multiple Objects in Batches
We often need to iterate over a large set of records, as when we send a newsletter to a large set of users, or when we export data.