In recent versions, you can do "select count(distinct theCol) ..." (I'm actually running one at this moment!!)
On Mon, 2002-03-04 at 09:34, Rob wrote: > Given a table with some non-unique column theCol, what is the most efficient > way to count the number of different values in theCol? I guess you can use a > temporary table as a subselect: > > CREATE TEMPORARY TABLE tmp SELECT UNIQUE theCol FROM theTable; > SELECT COUNT(*) FROM tmp; > DROP TABLE tmp; > > But this seem obscenely inefficient- it's a situation just screaming out for > a summary function: > > SELECT COUNT_UNIQUE(theCol) FROM theTable; > > Does such a function exist in mySQL? Is one planned? > > Further, using the first method, what are the efficiency and robustness > differences between using 'SELECT UNIQUE theCol' and 'SELECT theCol GROUP BY > theCol'? > > > --------------------------------------------------------------------- > Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > > To request this thread, e-mail <[EMAIL PROTECTED]> > To unsubscribe, e-mail <[EMAIL PROTECTED]> > Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php > --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
