Seeks vs Scans
March 7th, 2010
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What is the difference between a seek and a scan? It can be quite a lot, actually!
By definition, a scan will touch on every row in the table or index and retrieve only those rows which match the query criteria. On the other hand, a seek will use available indexes to locate the data.
One thing to note is that I mentioned that a seek will use available indexes. While a table may have an index, SQL Server may still choose to perform a scan if the scan is considered less expensive – for example, a small table may be subject to a scan over a seek.
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