Hi, On Feb 15, 2008 10:26 AM, Price, Randall <[EMAIL PROTECTED]> wrote: > Since both of these work, I was wondering which one would be faster. > > Here is an EXPLAIN on a similar test I did on one of my test tables. > > (NO index on field1, WinXP, MySQL 5.0.41-community-nt, SQLyog query > window) > > > SELECT COUNT(*) FROM tblClients > (1660 row(s) returned) > (0 ms taken) > > RESET QUERY CACHE > > SELECT DISTINCT field1 FROM tblClients > (130 row(s) returned) > (0 ms taken) > > > EXPLAIN SELECT DISTINCT field1 FROM tblClients > /* 1457 rows, Using temporary */ > > > RESET QUERY CACHE > > SELECT field1 FROM tblClients GROUP BY field1 > (130 row(s) returned) > (16 ms taken) > > > EXPLAIN SELECT field1 FROM tblClients GROUP BY field1 > /* 1457 rows, Using temporary; Using filesort */ > > > It appears that the SELECT DISTINCT did not have to use the filesort. > So that should be faster, which confirms what I see here.
That's because MySQL automatically sorts GROUP BY queries by the group-by columns. If you add ORDER BY NULL, the two queries should be exactly equivalent. But I'd just use DISTINCT :-) Baron -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
