Home Forums SQL Server 2008 SQL Server 2008 - General Understanding the difference between Join and Where filters - SQL 2008R2 RE: Understanding the difference between Join and Where filters - SQL 2008R2

  • September 24, 2012 at 8:06 am

    #1541416

    laurie-789651 (9/24/2012)

    2. You could consider using

    FROM Table1 SD WITH (NOLOCK) JOIN Table2 WITH (NOLOCK) etc.

    as long as the table isn't being updated - this saves time as no read locks are issued.

    And incorrect results are possible, not just dirty reads, duplicate or missing rows. If there are no changes being made, there's little gain from nolock, the overhead of taking locks is not that high, and it introduces the potential for incorrect results when changes are being made.

    See - http://blogs.msdn.com/b/davidlean/archive/2009/04/06/sql-server-nolock-hint-other-poor-ideas.aspx

    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

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