Which SQL statement is faster? (HAVING vs. WHERE…)

Question

SELECT NR_DZIALU, COUNT (NR_DZIALU) AS LICZ_PRAC_DZIALU
    FROM  PRACOWNICY
    GROUP BY NR_DZIALU
    HAVING NR_DZIALU = 30

or

SE         


        

Answer 1

"WHERE" is faster than "HAVING"!

The more complex grouping of the query is - the slower "HAVING" will perform to compare because: "HAVING" "filter" will deal with larger amount of results and its also being additional "filter" loop

"HAVING" will also use more memory (RAM)

Altho when working with small data - the difference is minor and can absolutely be ignored

Answer 2

Both the statements will be having same performance as SQL Server is smart enough to parse both the same statements into a similar plan.

So, it does not matter if you use WHERE or HAVING in your query.

But, ideally you should use WHERE clause syntactically.