Side Effects Of Selects

Paul Randal describes a few things that can change behind the scenes when you run a SELECT query:

Statistics Update

If the database property Auto Update Statistics is set to True, when a query is being compiled and a necessary statistic is determined to be out-of-date, it will be automatically updated before optimization continues, thus changing the database. Your SELECT statement could cause this to happen. Additionally, if the Auto Update Statistics Asynchronously property is enabled, the statistic will be automatically updated, but after the optimization process (so the compiling query doesn’t have to wait).

Read on for a few more activities.

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