Arvind Yadav
What are statistics, under what circumstances do they go out of date, how do you update them?

What are statistics, under what circumstances do they go out of date, how do you update them?

By Arvind Yadav in SQL on Feb 24 2022
  • Gajendra Jangid
    Mar, 2022 10

    Statistics determine the selectivity of the indexes. If an
    indexed column has unique values then the selectivity of
    that index is more, as opposed to an index with non-unique
    values. Query optimizer uses these indexes in determining
    whether to choose an index or not while executing a query.

    Some situations under which you should update statistics:
    1) If there is significant change in the key values in the
    index
    2) If a large amount of data in an indexed column has been
    added, changed, or removed (that is, if the distribution of

    key values has changed), or the table has been truncated
    using the TRUNCATE TABLE statement and then repopulated
    3) Database is upgraded from a previous version

    • 1


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