Re: Deadly sins againts database performance/scalability

Alkos wrote:

> Most of the time, people use SELECT DISTINCT to get unique rows because
> they don't want to "bother" with the datamodel. They are lazy or hurried so
> they don't care about possible
> keys, about WHERE clauses selectivity and all that kind of things so quick
> and dirty solution to be sure to get unique rows : SELECT DISTINCT which
> implies a sort therefore more activity to get the same result as they may
> have gotten quicker with a little bit work on the WHERE clause.

I do use SELECT DISTINCT when I have just to pick up distinct values from a table, and I don't need to count them or performing group functions amongs columns in the table. I assume the performance of this statement:

SELECT DISTINCT FOOCOL FROM FOOTAB ; is better than the performance of this one:

SELECT FOOCOL, COUNT(FOOCOL) FROM FOOTAB GROUP BY FOOCOL ; Or am I wrong?

-- 
Cris Carampa (spamto:cris119_at_operamail.com)

"Poveri fanatici comunisti, noglobal e affetti dalla sindrome
anti-microsoft" (gli utenti Linux secondo un poster di ICOD)