Correct the limitation about order with distinct in the guide

That is happened with `distinct`, and that is not only happened on MyS
L, but also on PostgreSQL, SQL Server, and Oracle.

[ci skip]

guides/source/active_record_querying.md

@@ -611,7 +611,8 @@ If you want to call `order` multiple times, subsequent orders will be appended t
 Client.order("orders_count ASC").order("created_at DESC")
 # SELECT * FROM clients ORDER BY orders_count ASC, created_at DESC
 ```
-WARNING: If you are using **MySQL 5.7.5** and above, then on selecting fields from a result set using methods like `select`, `pluck` and `ids`; the `order` method will raise an `ActiveRecord::StatementInvalid` exception unless the field(s) used in `order` clause are included in the select list. See the next section for selecting fields from the result set.
+
+WARNING: In most database systems, on selecting fields with `distinct` from a result set using methods like `select`, `pluck` and `ids`; the `order` method will raise an `ActiveRecord::StatementInvalid` exception unless the field(s) used in `order` clause are included in the select list. See the next section for selecting fields from the result set.
 
 Selecting Specific Fields
 -------------------------