How to find out the identity coloumn of a table.

  • Hi,

     

    I want to drop the identity property of a coloumn in a table.But i dont know the column which has the identity property.

    so please let me know How to find out the idntity column and how to drop the identity property of that coloumn.

    ThanQ.

  • SELECT identitycol FROM WhatEverTable WHERE 1 = 0


    N 56°04'39.16"
    E 12°55'05.25"

  • ThanQ for the solution.

    But i want to drop the identity property of that coloumn.

    How can i do it in TSQL. please let me know.

     

  • Hi,

    hope it will help you

    ------------------------------------------

    declare @TblName sysname

    set @tblName = 'Your table name'

    -- show identity col name

    select syscolumns.name from sysobjects

    inner join syscolumns on sysobjects.id = syscolumns.id

    where sysobjects.name = @tblName and syscolumns.status = 0x80

    -- show identity constraint name

    select sysobjconstraint.name from sysobjects

    inner join sysconstraints on sysobjects.id = sysconstraints.id

    left outer join sysobjects sysobjconstraint on sysconstraints.constid = sysobjconstraint.id

    where sysobjects.name = @tblName and sysobjconstraint.xtype = 'PK'

    ---------------------------------------------

    use the resultset into ALTER TABLE DROP CONSTRAINTS but be carefull with FK, for detecting FK take a look at sysforeignkeys table

  • there's a difference between a primary key, which technically can span multiple columns, and a column that has the identity function on it to auto generate the next value of the table;

    there can be only one column in a table where the autoval is not null(which identifies it as the column that was created with identity)

     

    with both the drop constraint for the PK and the alter table to remove the identity(), i think that's the tools you need.

    here i'm expanding Gracia's example to include that as well:

    declare @TblName sysname

    set @tblName = 'GMACT'

    -- show identity col name

    select

     'ALTER TABLE '

      + @tblName

      + ' ALTER COLUMN '

      + UPPER(syscolumns.name)

      + SPACE(2)

      + UPPER(TYPE_NAME(syscolumns.xtype))

      --this is for the original definition

      --+ SPACE(12 - LEN(TYPE_NAME(syscolumns.xtype))) + CASE WHEN syscolumns.autoval IS NULL THEN '              ' ELSE ' IDENTITY(1,1)' END

      + SPACE(2) + CASE WHEN syscolumns.isnullable=0 THEN  ' NOT NULL' ELSE '     NULL' END AS ORIGINAL_DEFINITION,

    syscolumns.name from sysobjects

    inner join syscolumns on sysobjects.id = syscolumns.id

    where sysobjects.name = @tblName and autoval is not null

    -- show identity constraint name

    select 'ALTER TABLE ' + @tblName + ' DROP CONSTRAINT ' + sysobjconstraint.name  AS DROP_STATEMENT,sysobjconstraint.name from sysobjects

    inner join sysconstraints on sysobjects.id = sysconstraints.id

    left outer join sysobjects sysobjconstraint on sysconstraints.constid = sysobjconstraint.id

    where sysobjects.name = @tblName and sysobjconstraint.xtype = 'PK'

    --select * from syscolumns where autoval is not null

     

    results:

    ORIGINAL_DEFINITION                                      

    ----------------------------------------------------------

    ALTER TABLE GMACT ALTER COLUMN ACTTBLKEY  INT   NOT NULL 

                                                             

    DROP_STATEMENT                                           

    ----------------------------------------------------------

    ALTER TABLE GMACT DROP CONSTRAINT PK__GMACT__1E05700A    

    Lowell


    --help us help you! If you post a question, make sure you include a CREATE TABLE... statement and INSERT INTO... statement into that table to give the volunteers here representative data. with your description of the problem, we can provide a tested, verifiable solution to your question! asking the question the right way gets you a tested answer the fastest way possible!

Viewing 5 posts - 1 through 4 (of 4 total)

You must be logged in to reply to this topic. Login to reply