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Difference between Count(*) & Count(1)

  • May 14, 2009 at 2:52 am

    #99692

    What is the difference between Count(*),Count(1).... in sql server

    ?

    for ex. A table contains 100

    select count(*) from emp

    select count(1) from emp

    select count(2) from emp

    All the three queries display the same result .then what is the difference between them?

    Tanx 😀

  • May 14, 2009 at 3:47 am

    #994342

    No practical difference. They both count the number of rows in the resultset.

    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

  • May 14, 2009 at 4:06 am

    #994349

    select count(*) from table

    and

    select count(1) from table

    will return the same results, but

    select count(column name) from table

    will return the number of non null columns

  • May 14, 2009 at 4:56 am

    #994366

    SeanF (5/14/2009)

    select count(column name) from table

    will return the number of non null columns

    More correctly it will return the number of rows in the table where the column specified is not null.

    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

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