How to Retrieve Newly Generated Identity Values in SQL Server?

SQL Server Identity Value Retrieval Methods: A Comprehensive Guide

When working with SQL Server tables containing identity columns, retrieving the newly generated identity value after an insert operation is crucial. This guide explores the various functions and techniques available for this purpose: @@IDENTITY, IDENT_CURRENT, SCOPE_IDENTITY(), and the OUTPUT clause.

Understanding the Options

Each method offers a different level of scope and reliability:

• @@IDENTITY: This function returns the last identity value generated within the current session, regardless of the specific table or statement. While simple to use, its broad scope makes it susceptible to errors if multiple inserts occur within the same session. Use with caution.

• IDENT_CURRENT('tableName'): This function specifically targets a given table (tableName), retrieving the last identity value generated for that table across all sessions and scopes. It's less frequently used but provides a higher degree of specificity than @@IDENTITY.

• SCOPE_IDENTITY(): This is generally the preferred method. It returns the last identity value generated within the current session and the current scope (typically, the current batch or stored procedure). This provides better isolation and accuracy compared to @@IDENTITY.

• OUTPUT Clause: The OUTPUT clause, used with the INSERT statement, provides a powerful and reliable way to capture the identity values of all inserted rows. The inserted rows are written to a temporary table or table variable, allowing you to directly query the identity values. This is particularly beneficial when dealing with parallel execution plans. However, note that the OUTPUT clause executes before triggers, meaning it won't reflect identity values generated by triggers.

Choosing the Right Method

For most scenarios, SCOPE_IDENTITY() offers the best balance of simplicity and reliability. @@IDENTITY should be avoided unless its broader scope is explicitly required. IDENT_CURRENT('tableName') provides a more specific approach when needed, and the OUTPUT clause is valuable for its robustness, particularly in complex scenarios or when working with parallel processing. The choice ultimately depends on the specific requirements of your application and the potential for concurrent operations.

The above is the detailed content of How to Retrieve Newly Generated Identity Values in SQL Server?. For more information, please follow other related articles on the PHP Chinese website!