IO Statistics Vs Table Statistics - SQL Server 2005

Posted on 2010-01-06
Last Modified: 2012-08-13

Please let me know what is the difference between table Statistics & IO Statistics.

1. As per my knowledge Table Statistics are updated automatically (If Database option is set to True). But what about IO Statistics?

2. When we rebuild index table Statistics are also updated?
3. If IO Statistics and  Table Statistics are different, then how to update  IO Statistics?


Question by:srinivas_ganamur
    LVL 10

    Accepted Solution


    In simple terms:

    Table Statistics are information about the table consisting of things like (number of rows and pages occupied by data, selectivity of columns, information about indexes and such) and it is used by optimiser to boot the query performance automatically.

    IO Statistics are information about single query and how it get's the data. You may use it to improve the query design manually.

    1. IO Statistics are generated each time you run a query if the option STATISTICS IO is set to ON.
    2. As far as I know (but here I might be wrong) Statistics are not updated when you rebuild an index.
    3. You don't need to update them as they are not stored. See point 1.

    Author Comment

    Hi Experts,

    any comments on Point 2 and 3

    2. As far as I know (but here I might be wrong) Statistics are not updated when you rebuild an index.
    3. You don't need to update them as they are not stored. See point 1.
    LVL 10

    Expert Comment

    3 is for sure. IO Statistics does not need bo be updates so there is no way to do it.

    2 is something I am not sure. Nowhere on MS documentation I can see information about statistics updates and index rebuilding to be related in any way so I assume they are not. That means rebuilding index does include updating statistics.

    Author Closing Comment


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