http://ift.tt/1FIolgv
Index Seek and Index (or Table) Scan are two of the most common operators that you see in query execution plans. A common misconception is that a scan is bad and a seek is good. The reality is that each is optimal under different circumstances. In some cases the optimizer chooses between the two based on which is indeed more optimal in the given situation. In those cases, other than appreciating the optimizer's ability to come up with the truly optimal plan, there's nothing special that we need to do. However, what's interesting to us as people who tune queries is to identify cases, or patterns, in which the optimizer doesn't make the optimal choice and act to fix them.
from SQL Server Pro http://ift.tt/1kCjeYg
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