IDENT_CURRENT (Transact-SQL)

Artigo
12/03/2008

Returns the last identity value generated for a specified table or view in any session and any scope.

Topic link icon Transact-SQL Syntax Conventions

Syntax

IDENT_CURRENT( 'table_name' )

Arguments

table_name
Is the name of the table whose identity value is returned. table_name is varchar, with no default.

Return Types

numeric(38,0)

Exceptions

Returns NULL on error or if a caller does not have permission to view the object.

In SQL Server 2005, a user can only view the metadata of securables that the user owns or on which the user has been granted permission. This means that metadata-emitting, built-in functions such as IDENT_CURRENT may return NULL if the user does not have any permission on the object. For more information, see Metadata Visibility Configuration and Troubleshooting Metadata Visibility.

Remarks

IDENT_CURRENT is similar to the SQL Server 2000 identity functions SCOPE_IDENTITY and @@IDENTITY. All three functions return last-generated identity values. However, the scope and session on which last is defined in each of these functions differ:

IDENT_CURRENT returns the last identity value generated for a specific table in any session and any scope.
@@IDENTITY returns the last identity value generated for any table in the current session, across all scopes.
SCOPE_IDENTITY returns the last identity value generated for any table in the current session and the current scope.

The IDENT_CURRENT function returns NULL when the function is invoked on an empty table or on a table that has no identity column.

Failed statements and transactions can change the current identity for a table and create gaps in the identity column values. The identity value is never rolled back even though the transaction that tried to insert the value into the table is not committed. For example, if an INSERT statement fails because of an IGNORE_DUP_KEY violation, the current identity value for the table is still incremented.

Be cautious about using IDENT_CURRENT to predict the next generated identity value. The actual generated value may be different from IDENT_CURRENT plus IDENTITY_SEED because of insertions performed by other sessions.

Examples

A. Returning the last identity value generated for a specified table

The following example returns the last identity value generated for the Person.Address table in the AdventureWorks database.

USE AdventureWorks;
GO
SELECT IDENT_CURRENT ('Person.Address') AS Current_Identity;
GO

B. Comparing identity values returned by IDENT_CURRENT, @@IDENTITY and SCOPE_IDENTITY

The following example shows the different identity values that are returned by IDENT_CURRENT, @@IDENTITY, and SCOPE_IDENTITY.

USE AdventureWorks;
GO
IF OBJECT_ID(N't6', N'U') IS NOT NULL 
    DROP TABLE t6;
GO
IF OBJECT_ID(N't7', N'U') IS NOT NULL 
    DROP TABLE t7;
GO
CREATE TABLE t6(id int IDENTITY);
CREATE TABLE t7(id int IDENTITY(100,1));
GO
CREATE TRIGGER t6ins ON t6 FOR INSERT 
AS
BEGIN
   INSERT t7 DEFAULT VALUES
END;
GO
--End of trigger definition

SELECT id FROM t6;
--id is empty.

SELECT id FROM t7;
--ID is empty.

--Do the following in Session 1
INSERT t6 DEFAULT VALUES;
SELECT @@IDENTITY;
/*Returns the value 100. This was inserted by the trigger.*/

SELECT SCOPE_IDENTITY();
/* Returns the value 1. This was inserted by the 
INSERT statement two statements before this query.*/

SELECT IDENT_CURRENT('t7');
/* Returns value inserted into t7, that is in the trigger.*/

SELECT IDENT_CURRENT('t6');
/* Returns value inserted into t6. This was the INSERT statement four statements before this query.*/

-- Do the following in Session 2.
SELECT @@IDENTITY;
/* Returns NULL because there has been no INSERT action 
up to this point in this session.*/

SELECT SCOPE_IDENTITY();
/* Returns NULL because there has been no INSERT action 
up to this point in this scope in this session.*/

SELECT IDENT_CURRENT('t7');
/* Returns the last value inserted into t7.*/

Change History

Release	History
17 July 2006	New content: Added the "Exceptions" section.
14 April 2006	New content: Added a sentence that cautions about using IDENT_CURRENT to predict the next identity value.

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