Federico Schwindt wrote: > hi, > > i'm not sure if this belongs here, but i cannot seem to find the > answer anywhere else. > first, what's the difference between: > > PRIMARY KEY (key1, key2) > PRIMARY KEY (key1), KEY (key2)
The first line creates a single, unique key on the columns key1 and key2. The second line creates two keys, the first a unique key on key1 and the second on just key2 that allows duplicates. > second, let's suppose the following table: > > owner_id int(11), > customer_id int(11), > customer_info varchar(100) > > and i want to search either by owner_id and customer_id. > can i do this w/o creating the indexes by hand? or do i have to > create'em explicity and specify which one i'm gonna use before > performing a query? You never need keys to query a table. It just makes the query much faster. For a query like "WHERE owner_id=X AND custoerm_id=Y" you would want a composite index on both columns, e.g. KEY( owner_id, customer_id ). This key would also cover a query that had just "WHERE owner_id=X". If, then, you wanted to query on just the customer_id, you would want to add another key on just customer_id. E.g.: CREATE TABLE tbl ( owner_id int(11), customer_id int(11), customer_info varchar(100) key( owner_id, customer_id ), key( customer_id ) ); Of course, study the documentation for further explanation info. b. --------------------------------------------------------------------- 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
