Home Forums SQL Server 2008 T-SQL (SS2K8) Find potential locks caused by joined queries RE: Find potential locks caused by joined queries

  • August 1, 2013 at 2:32 pm

    #1637952

    Donnie Carvajal (8/1/2013)

    Thanks again.

    Is the goal to get the actual number of rows and estimated number of rows to be equal?

    Donnie

    within the same order of magnitude or so, doesn't have to be exact.

    the stats are used for deciding the best execution plan, and the optimizer uses them to produce the best plan it can in the microseconds it's allotted to do that in.

    inserts/updates/deletes modify the real data, but not the statistics about the data.

    Auto update of statistics requires 20% of the rows of the table + 500 more rows before SQL does it for you;

    but on a big table a much smaller percentage of rows modified can adversely affect query plans;

    20% of a MillionBillion Row table might not occur for a long time.

    Lowell

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