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IDENTITY (Function) (Transact-SQL)

  • Artikkeli

Applies to: SQL Server Azure SQL Managed Instance

Is used only in a SELECT statement with an INTO table clause to insert an identity column into a new table. Although similar, the IDENTITY function is not the IDENTITY property that is used with CREATE TABLE and ALTER TABLE.

Note

To create an automatically incrementing number that can be used in multiple tables or that can be called from applications without referencing any table, see Sequence Numbers.

Transact-SQL syntax conventions

Syntax

IDENTITY (data_type [ , seed , increment ] ) AS column_name

Arguments

data_type
Is the data type of the identity column. Valid data types for an identity column are any data types of the integer data type category, except for the bit data type, or decimal data type.

seed
Is the integer value to be assigned to the first row in the table. Each subsequent row is assigned the next identity value, which is equal to the last IDENTITY value plus the increment value. If neither seed nor increment is specified, both default to 1.

increment
Is the integer value to add to the seed value for successive rows in the table.

column_name
Is the name of the column that is to be inserted into the new table.

Return Types

Returns the same as data_type.

Remarks

Because this function creates a column in a table, a name for the column must be specified in the select list in one of the following ways:

--(1)  
SELECT IDENTITY(int, 1,1) AS ID_Num  
INTO NewTable  
FROM OldTable;  
  
--(2)  
SELECT ID_Num = IDENTITY(int, 1, 1)  
INTO NewTable  
FROM OldTable;

Examples

The following example inserts all rows from the Contact table from the AdventureWorks2022database into a new table called NewContact. The IDENTITY function is used to start identification numbers at 100 instead of 1 in the NewContact table.

USE AdventureWorks2022;  
GO  
IF OBJECT_ID (N'Person.NewContact', N'U') IS NOT NULL  
    DROP TABLE Person.NewContact;  
GO  
ALTER DATABASE AdventureWorks2022 SET RECOVERY BULK_LOGGED;  
GO  
SELECT  IDENTITY(smallint, 100, 1) AS ContactNum,  
        FirstName AS First,  
        LastName AS Last  
INTO Person.NewContact  
FROM Person.Person;  
GO  
ALTER DATABASE AdventureWorks2022 SET RECOVERY FULL;  
GO  
SELECT ContactNum, First, Last FROM Person.NewContact;  
GO

See Also

CREATE TABLE (Transact-SQL)
@@IDENTITY (Transact-SQL)
IDENTITY (Property) (Transact-SQL)
SELECT @local_variable (Transact-SQL)
DBCC CHECKIDENT (Transact-SQL)
sys.identity_columns (Transact-SQL)