How to Choose the Right SQL Server Identity Retrieval Function: @@IDENTITY, SCOPE_IDENTITY(), IDENT_CURRENT(), or OUTPUT?

SQL Server Identity Management: Choosing the Right Function (@@IDENTITY, SCOPE_IDENTITY(), IDENT_CURRENT(), OUTPUT)

Many database applications require access to the ID of newly inserted rows, especially when dealing with tables containing identity columns. SQL Server offers several ways to achieve this; each method has specific uses and potential drawbacks.

@@IDENTITY: Session-Wide Identity Retrieval

@@IDENTITY retrieves the last identity value generated in the current session, regardless of the table or scope. Caution is advised: @@IDENTITY can return values from other scopes (e.g., a trigger), potentially leading to inaccurate results.

SCOPE_IDENTITY(): Scope-Specific Identity Retrieval

SCOPE_IDENTITY() provides a more precise approach, returning the last identity value generated within the current session and scope (typically the current database). Its reliability makes it the preferred method for most scenarios. The scope can be further refined using the (n) syntax.

IDENT_CURRENT(): Table-Specific Identity Retrieval

IDENT_CURRENT('tableName') retrieves the last identity value generated for a specified table, irrespective of the session or scope. This is helpful when accessing identity values from a table not modified in the current session or when @@IDENTITY and SCOPE_IDENTITY() are unsuitable.

OUTPUT Clause: Statement-Level Identity Retrieval

The OUTPUT clause within an INSERT statement offers a direct way to access the IDs of inserted rows within the statement's scope. Unlike @@IDENTITY, it avoids cross-scope issues. However, it necessitates the use of table variables or temporary tables to store the output, potentially increasing complexity and impacting performance. Critically, it's the only guaranteed method for retrieving identities in parallel execution.

Selecting the correct identity retrieval method depends on the specific application needs. While SCOPE_IDENTITY() is generally recommended, @@IDENTITY, IDENT_CURRENT(), and the OUTPUT clause offer valuable alternatives in specific contexts.

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