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Must i use the property UNIQUE in a table auto-increment?

  • October 23, 2009 at 8:34 am

    #211336

    it's a simple question, i'm just learning and wanted know if is interesting use 'UNIQUE' in a table that is auto-increment? The values can't repeat

  • October 23, 2009 at 8:38 am

    #1070075

    You don't have to have a unique index on an identity column. It's pretty normal to do so, but not required. Is that what you're asking?

    To see this for yourself, try this:

    create table #T (

    ID int identity);

    set identity_insert #T on;

    insert into #T (ID)

    select 1 union all

    select 1;

    set identity_insert #T off;

    select *

    from #T;

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  • October 23, 2009 at 9:22 am

    #1070108

    Since the reason it is used tends to be so that there is a unique value for the record it is very normal to make it a unique index, often a clustered index..

    CEWII

  • October 23, 2009 at 9:42 am

    #1070125

    That's right, thank staff.

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