If you have an index consisting of member_id & mail_id (opposite order), you'll need just one index.
A good explanation of why may be found at: http://www.mysql.com/documentation/mysql/bychapter/manual_MySQL_Optimisation.html#Multiple-column_indexes -rh >I for sure need an index on the mail_id field (the primary key will be >between member_id and mail_id), so an index of mail_id AND member_id makes >sense. This index would work for queries like: > >WHERE mail_id = XXX >WHERE mail_id = XXX AND member_id = YYY > >However, that leaves out queries like: > >WHERE member_id = YYY > >That is also a query I need to be able to do on a regular basis, and if this >query yields 20,000 results, with 5 million rows in the table, it's going to >take forever (I assume). > >So I was thinking about making two indexes: > >mail_id AND member_id >member_id > >Would this take up way too much disk space? --------------------------------------------------------------------- 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
