Which is better: Distinct or Group By

Question

Which is more efficient?

SELECT  theField
FROM    theTable
GROUP BY theField

or

SELECT  DISTINCT theField
FROM    theTable
         


        

Answer 1

In your example, both queries will generate the same execution plan so their performance will be the same.

However, they both have their own purpose. To make your code easier to understand, you should use distinct to eliminate duplicate rows and group by to apply aggregate operators (sum, count, max, ...).