3. Key Lookups (15m)

So what is a key lookup? Well, the optimizer made a choice, for better or for worse, well apparently in this case for worse, where it used a non-clustered index to make part of a query more efficient, but that non-clustered index didn’t have all the columns the query needed. It could be missing columns…

To access this incredible, amazing content, you gotta get Fundamentals of Query Tuning or Recorded Class Season Pass, or log in if you already shelled out the cash.

So what is a key lookup? Well, the optimizer made a choice, for better or for worse, well apparently in this case for worse, where it used a non-clustered index to make part of a query more efficient, but that non-clustered index didn’t have all the columns the query needed. It could be missing columns...
To access this incredible, amazing content, you gotta get Fundamentals of Query Tuning or Recorded Class Season Pass, or log in if you already shelled out the cash.
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