----- Original Message ----- > From: "Alex Schaft" <al...@quicksoftware.co.za> > > If you have a table with columns A & B, and might do a where on A or > B, or an order by A, B, would single column indexes on A and B suffice > or would performance on the order by query be improved by an index on > A,B?
Depends on usage :-) key (a, b) is good for "where a=.." or "where a=.. and b=.." key (b, a) is good for "where b=.." or "where b=.. and a=.." (note that the sequence of a and b in the where clause is not important) key (a), key (b) is good for "where a=.." or "where b=.." but will only use one index for "where a=.. and b=..". I think work is ongoing on having the parser use multiple indices, but I'm not sure where that's at. -- Bier met grenadyn Is als mosterd by den wyn Sy die't drinkt, is eene kwezel Hy die't drinkt, is ras een ezel -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
