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SET SHOWPLAN_XML: EstimateRows and the EstimatedTotalSubtreeCost

Posted on 2011-03-10
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Last Modified: 2012-05-11
Hi experts, i am reading about SET SHOWPLAN_XML (Transact-SQL)
but i do not understand this line
 "The values in the EstimateRows and the EstimatedTotalSubtreeCost attributes are smaller for the first indexed query, indicating that it is processed much faster and uses fewer resources than the nonindexed query"

can you explain me?

I attached two file
query-1.jpg
query-2.jpg
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Question by:enrique_aeo
4 Comments
 
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Expert Comment

by:lcohan
ID: 35095571
Simply put a query using an index on a table.column is much faster and consumes less resources that a query (query2) that is NOT using an index.
To optimize query 2 you could add an index on Employee.Title column just make sure that you use LIKE with only one % as per above. What I mean is that a LIKE "%Production%' won't use an index even is you have one.
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by:enrique_aeo
ID: 35107081
ok, but it means the difference of values ¿¿of Estimated Subtree Cost and EstimateRows?
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Accepted Solution

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jogos earned 250 total points
ID: 35256686
Why difference in value?  It is not because your result is the same that SQL had the same effort to produce your result.

First query can find your result directly because  = on indexed columns
2nd query 'like' -> there are more records to evaluate before giving the result, probably same single record

meaning of 'estimate' is important
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