how to populate a new identity column on the target table using MERGE

  • I am using a merge to populate a target table. This table has a new column which takes identity values. All the other columns are populated with Source table data, so when it comes to this new column, I don't know how to handle.

    How do I get autoincremented values to populate an identity column on a MERGE statement?

  • correction, using the WHEN NOT MATCHED THEN INSERT portion of the MERGE statement, I want to insert values into the identity column.

  • you shouldn't have to explicitly insert a value into an identity column. The idea of the identity column is to auto increment - so when a new value is inserted into the table the value is inserted for you.

    In the merge statement just specify the columns that you want to insert excluding the identity column and that should work ok.

    Here's a little example:

    -- Create a test table

    CREATE TABLE TABLE1

    (

    id INT IDENTITY(1,1)

    ,custname VARCHAR(50)

    CONSTRAINT pk_table1 PRIMARY KEY CLUSTERED (id ASC)

    );

    -- Populate the table with some data

    INSERT INTO table1 (custname)

    VALUES('Mr'),

    ('Chris'),

    ('michael'),

    ('kerry'),

    ('gary'),

    ('adam'),

    ('wayne'),

    ('alan');

    -- select from the table to see a before snapshot

    SELECT * FROM table1;

    -- declare table variable to be used as a source table

    DECLARE @table2 TABLE

    (

    id INT IDENTITY(1,1)

    ,custname VARCHAR(50)

    );

    -- populate the source table

    INSERT INTO @table2 (custname)

    VALUES('Mr'),

    ('Christopher'),

    ('Michael'),

    ('Kerry'),

    ('Gary'),

    ('adam'),

    ('wayner'),

    ('alan');

    -- Merge source to target

    MERGE INTO table1 tgt

    USING @table2 src

    ON tgt.custname = src.custname

    WHEN MATCHED THEN

    UPDATE SET

    tgt.id = tgt.id + 1

    WHEN NOT MATCHED THEN

    INSERT (custname)

    VALUES (src.custname);

    -- select from the table to see after snapshot

    SELECT * FROM table1;

    Hope this helps..

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