Redigera

Dela via

SCOPE_IDENTITY (Transact-SQL)

  • Artikel

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

Returns the last identity value inserted into an identity column in the same scope. A scope is a module: a stored procedure, trigger, function, or batch. Therefore, if two statements are in the same stored procedure, function, or batch, they are in the same scope.

Transact-SQL syntax conventions

Syntax

SCOPE_IDENTITY()

Return Types

numeric(38,0)

Remarks

SCOPE_IDENTITY, IDENT_CURRENT, and @@IDENTITY are similar functions because they return values that are inserted into identity columns.

IDENT_CURRENT is not limited by scope and session; it is limited to a specified table. IDENT_CURRENT returns the value generated for a specific table in any session and any scope. For more information, see IDENT_CURRENT (Transact-SQL).

SCOPE_IDENTITY and @@IDENTITY return the last identity values that are generated in any table in the current session. However, SCOPE_IDENTITY returns values inserted only within the current scope; @@IDENTITY is not limited to a specific scope.

For example, there are two tables, T1 and T2, and an INSERT trigger is defined on T1. When a row is inserted to T1, the trigger fires and inserts a row in T2. This scenario illustrates two scopes: the insert on T1, and the insert on T2 by the trigger.

Assuming that both T1 and T2 have identity columns, @@IDENTITY and SCOPE_IDENTITY return different values at the end of an INSERT statement on T1. @@IDENTITY returns the last identity column value inserted across any scope in the current session. This is the value inserted in T2. SCOPE_IDENTITY() returns the IDENTITY value inserted in T1. This was the last insert that occurred in the same scope. The SCOPE_IDENTITY() function returns the null value if the function is invoked before any INSERT statements into an identity column occur in the scope.

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.

Examples

A. Using @@IDENTITY and SCOPE_IDENTITY with triggers

The following example creates two tables, TZ and TY, and an INSERT trigger on TZ. When a row is inserted to table TZ, the trigger (Ztrig) fires and inserts a row in TY.

USE tempdb;  
GO  
CREATE TABLE TZ (  
   Z_id  INT IDENTITY(1,1)PRIMARY KEY,  
   Z_name VARCHAR(20) NOT NULL);  
  
INSERT TZ  
   VALUES ('Lisa'),('Mike'),('Carla');  
  
SELECT * FROM TZ;

Result set: This is how table TZ looks.

Z_id   Z_name  
-------------  
1      Lisa  
2      Mike  
3      Carla  

CREATE TABLE TY (  
   Y_id  INT IDENTITY(100,5)PRIMARY KEY,  
   Y_name VARCHAR(20) NULL);  
  
INSERT TY (Y_name)  
   VALUES ('boathouse'), ('rocks'), ('elevator');  
  
SELECT * FROM TY;

Result set: This is how TY looks:

Y_id  Y_name  
---------------  
100   boathouse  
105   rocks  
110   elevator

Create the trigger that inserts a row in table TY when a row is inserted in table TZ.

CREATE TRIGGER Ztrig  
ON TZ  
FOR INSERT AS   
   BEGIN  
   INSERT TY VALUES ('')  
   END;

FIRE the trigger and determine what identity values you obtain with the @@IDENTITY and SCOPE_IDENTITY functions.

INSERT TZ VALUES ('Rosalie');  
  
SELECT SCOPE_IDENTITY() AS [SCOPE_IDENTITY];  
GO  
SELECT @@IDENTITY AS [@@IDENTITY];  
GO

Here's the result set.

/*SCOPE_IDENTITY returns the last identity value in the same scope. This was the insert on table TZ.*/`  
SCOPE_IDENTITY  
4  

/*@@IDENTITY returns the last identity value inserted to TY by the trigger. 
  This fired because of an earlier insert on TZ.*/
@@IDENTITY  
115

B. Using @@IDENTITY and SCOPE_IDENTITY() with replication

The following examples show how to use @@IDENTITY and SCOPE_IDENTITY() for inserts in a database that is published for merge replication. Both tables in the examples are in the AdventureWorks2022 sample database: Person.ContactType is not published, and Sales.Customer is published. Merge replication adds triggers to tables that are published. Therefore, @@IDENTITY can return the value from the insert into a replication system table instead of the insert into a user table.

The Person.ContactType table has a maximum identity value of 20. If you insert a row into the table, @@IDENTITY and SCOPE_IDENTITY() return the same value.

USE AdventureWorks2022;  
GO  
INSERT INTO Person.ContactType ([Name]) VALUES ('Assistant to the Manager');  
GO  
SELECT SCOPE_IDENTITY() AS [SCOPE_IDENTITY];  
GO  
SELECT @@IDENTITY AS [@@IDENTITY];  
GO

Here's the result set.

SCOPE_IDENTITY  
21  
@@IDENTITY  
21

The Sales.Customer table has a maximum identity value of 29483. If you insert a row into the table, @@IDENTITY and SCOPE_IDENTITY() return different values. SCOPE_IDENTITY() returns the value from the insert into the user table, whereas @@IDENTITY returns the value from the insert into the replication system table. Use SCOPE_IDENTITY() for applications that require access to the inserted identity value.

INSERT INTO Sales.Customer ([TerritoryID],[PersonID]) VALUES (8,NULL);  
GO  
SELECT SCOPE_IDENTITY() AS [SCOPE_IDENTITY];  
GO  
SELECT @@IDENTITY AS [@@IDENTITY];  
GO

Here's the result set.

SCOPE_IDENTITY  
29484  
@@IDENTITY  
89

See Also

@@IDENTITY (Transact-SQL)