


What are the differences between `SCOPE_IDENTITY()`, `IDENTITY()`, `@@IDENTITY`, and `IDENT_CURRENT()` in SQL Server?
In-depth understanding of the SCOPE_IDENTITY()
, IDENTITY()
, @@IDENTITY
and IDENT_CURRENT()
functions in SQL Server
The four functions SCOPE_IDENTITY()
, IDENTITY()
, @@IDENTITY
and IDENT_CURRENT()
are all used to retrieve auto-increment column values in SQL Server, but their uses are different. Let’s dive into their differences.
SCOPE_IDENTITY()
SCOPE_IDENTITY()
Retrieve the last inserted auto-increment column value in the current scope, which can be the current statement or batch. It does not consider auto-incrementing column values generated in other scopes within the same session.
IDENTITY()
Contrary to the name, IDENTITY()
is not used to retrieve auto-incrementing column values. It is used in SELECT...INTO
statements to create auto-increment columns when deriving a new table from data in another table.
@@IDENTITY
@@IDENTITY
Retrieves the last inserted auto-increment column value in the current session, regardless of its scope. This means that it includes auto-incrementing column values generated in the current scope and other scopes during the same session.
IDENT_CURRENT()
IDENT_CURRENT()
is a less used function designed to retrieve the last inserted auto-increment column value in a specific table or view, even across sessions.
When to use each function?
Generally, SCOPE_IDENTITY()
is preferred because it provides isolation within the current scope. If you need to reference an auto-increment column value generated in a parent statement or stored procedure in the same scope, SCOPE_IDENTITY()
ensures its accuracy.
@@IDENTITY
Useful when accessing auto-increment column values generated in other scopes within the session. For example, you can use it in a trigger or batch job when multiple operations occur in the same session.
IDENT_CURRENT()
is mainly used in scenarios where you need to access auto-increment column values in a specific table across multiple sessions, such as when connecting data from different data sources.
Example:
Consider the following code snippet:
-- 向'Customers'表插入一条记录 INSERT INTO Customers (Name) VALUES ('John Doe'); -- 检索当前语句中生成的自增列值 SELECT SCOPE_IDENTITY(); -- 触发器触发并插入另一条记录 CREATE TRIGGER InsertAudit ON Customers AFTER INSERT AS INSERT INTO AuditLog (CustomerId, Action) VALUES (@@IDENTITY, 'INSERT'); -- 检索触发器生成的自增列值 SELECT @@IDENTITY;
In this example, SCOPE_IDENTITY()
will return the auto-increment column value of the record inserted into the "Customers" table, while @@IDENTITY
will return the auto-increment column value created by the trigger after the audit log entry is inserted. This demonstrates how different scopes can lead to different results using @@IDENTITY
.
The above is the detailed content of What are the differences between `SCOPE_IDENTITY()`, `IDENTITY()`, `@@IDENTITY`, and `IDENT_CURRENT()` in SQL Server?. For more information, please follow other related articles on the PHP Chinese website!

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