Which SQL Server Identity Value Retrieval Method (@@IDENTITY, IDENT_CURRENT, SCOPE_IDENTITY, OUTPUT Clause) Should I Use?

SQL Server Identity Value Retrieval: A Practical Guide

SQL Server offers several ways to get the identity of a newly inserted row. Each method has its strengths and weaknesses, making the choice dependent on your specific needs. This guide clarifies the differences between @@IDENTITY, IDENT_CURRENT, SCOPE_IDENTITY, and the OUTPUT clause.

Comparing @@IDENTITY, IDENT_CURRENT, and SCOPE_IDENTITY

• @@IDENTITY: This function returns the last identity value generated in the current session, regardless of the table. Useful for retrieving the ID from any table within the session, but be wary: it can be affected by triggers or concurrent operations.

• IDENT_CURRENT: Retrieves the last identity value generated for a specific table, regardless of the session or scope. Ideal when you need the ID for a particular table, even if you didn't insert the row directly.

• SCOPE_IDENTITY: Returns the last identity value generated within the current session and scope. Generally the best choice for retrieving the ID of a recently inserted row because it's isolated from other concurrent processes within the same statement.

The OUTPUT Clause: A Powerful Alternative

The OUTPUT clause provides a direct way to access inserted rows from an INSERT statement. You can capture identity values, along with other column data, into a table variable or temporary table. While straightforward, it's slightly more complex to use and returns data even if the statement rolls back. Crucially, it executes before triggers, so it won't retrieve trigger-generated identity values. However, it offers the only reliable way to obtain identity values when using parallel processing, guaranteeing their availability regardless of the execution plan.

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