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Sql server indexes
In a SQL Server Execution plan what is the difference between an Index Scan and an Index Seek
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If you look at the properties for the operator it will explain what each one does. A scan looks at all or a significant part of a table or index. A seek looks at a more limited range of the index. The scan generally walks the pages where as a seek generally uses the key structure to find information. That's it in a nutshell.
And you missed the chance to pimp your [SQL Server Execution Plan][1] book... ;-) [1]:
http://www.red-gate.com/community/books/sql-server-execution-plans-ed-2
ha! Or, I didn't feel like looking up the URL. Thanks for posting it.
In a nut shell, an index scan will look (scan) the whole table/index and the the index seek will only look at pages that contain the rows that meet the criteria of the query (IE: where clause). Pinal Dave has a good explanation for this:
http://blog.sqlauthority.com/2007/03/30/sql-server-index-seek-vs-index-scan-table-scan/ Hope this helps!
Although, a scan can look at a subset of the data and a seek could end up seeking against the entire table/index. SQL Server is fun!
Index seek: Because your query is selective enough, you can go directly to the items you need through the index. Example: SELECT * FROM Employee WHERE EmpID = 12345 Index scan: Because your query isn't quite selective enough, so the whole index is being run through to find out which rows are required.
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