Tuesday, February 14, 2012

Clustered Indexes - High or Low Selectivity?

Hi,

I am studying for MCTS and through some of the course material it recommends that a low selectivity field i.e. First Name is a good canditate for a clustered index.

This goes against what is recommended online (completely the opposite) and goes against what I have been taught in the past.

What is correct for the exam?

Thanks

I often find various printed 'study' media with errors. Mark this one as just that.

Indexes, both clustered and non-clustered, may lose their effectiveness when selectivity becomes too low. The Query Processor may ignore a low selectivity index.

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