How to Retrieve the Last Identity Value in SQL Server: @@IDENTITY vs. SCOPE_IDENTITY() vs. OUTPUT?

Retrieving Last Identity Value: Methods and Scope

When working with tables that leverage primary key identities, developers often encounter the need to retrieve the value of the newly inserted identity. While various methods exist for this task, scoping and performance considerations play a crucial role in determining the appropriate approach.

@@IDENTITY vs. SCOPE_IDENTITY()

Both @@IDENTITY and SCOPE_IDENTITY() retrieve the last identity value produced within a connection. However, @@IDENTITY is not scope-bound and can return identities produced by previous queries or triggers, regardless of their scope. On the other hand, SCOPE_IDENT TY() limits its scope to the specific connection and query where the identity was generated, ensuring that it returns only the desired value.

OUTPUT Method

The OUTPUT clause can be used to retrieve identities within an INSERT statement. By including it in the query, the newly created identity value can be returned alongside other inserted columns. This approach is convenient but may lead to reduced performance in cases where only the identity value is required.

Choosing the Proper Method

The choice of method depends on the specific requirements of the application:

• @@IDENTITY: Most suitable when the most recent identity value, regardless of scope, is needed.
• SCOPE_IDENTITY(): Ideal when the identity value must be confined to a specific scope or query.
• IDENT_CURRENT(): Useful when the identity value for a specific table is required, regardless of connection or scope.

Scope-Safety of OUTPUT Method

The OUTPUT method is scope-safe, meaning it returns only identities generated by the current query in the same session. It does not retrieve identities produced by other queries or triggers. This ensures data integrity and prevents unintended side effects.

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