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
