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Difference between DISTINCT and GROUP BY


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Add Date: 11/13/2011
Here explaning Difference between DISTINCT and GROUP BY
A DISTINCT and GROUP BY usually generate the same query plan, so performance should be the same across both query constructs. GROUP BY should be used to apply aggregate operators to each group. If all you need is to remove duplicates then use DISTINCT. If you are using sub-queries execution plan for that query varies so in that case you need to check the execution plan before making decision of which is faster.

Example of DISTINCT:
Example of GROUP BY:

Example of GROUP BY with aggregate function:

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