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update query...

  • July 18, 2005 at 4:05 am

    #102644

    Hi all: I'm stuck with a problem. I have a table with 2 cloumns say 'A' and 'B'. I have to update the values of 'B' with the corresponding 'A' value whenever 'B' is 'null'. How do i write it in a single update statement? How do I refer the value of the corresponding 'A' that is satisfying the 'where' condition.

    update <table> set B=<'A' value of corresponding record> where B is null

  • July 18, 2005 at 5:07 am

    #575158

    Unless I'm misunderstanding...

    Update tbl set B=A where B IS NULL

    tbl Before

    AB
    1a
    2NULL
    3NULL
    4d

    tbl After

    AB
    1a
    22
    33
    4d

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

  • July 18, 2005 at 5:55 am

    #575164

    thanx bud: thats wat i had in mind too. but wanted to confirm it b4 updating it on the live database. i think i shld have a backup in future.

  • July 18, 2005 at 6:22 am

    #575168

    I think you should get a dev/playground database where you can try stuff out before running on live.

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

  • July 18, 2005 at 8:08 am

    #575211

    Quote:

    i think i shld have a backup in future.

    I think you should have a backup NOW!

    -SQLBill

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