John, As far as I'm aware there is no problem creating a multi-column unique index on fields that have already been indexed seperately. The multi column index will be used in situations where you are trying to find unique _combinations_ of the two fields and the individual indexes in situations where you are trying to find instances of one OR the other.
If you are doing a number of inserts or multi-row inserts you may want to use the "IGNORE" parameter. This will allow the INSERT command to complete and return successfully, simply skipping the rows where dupes are found, otherwise mysql is going to generate a duplicate key error when duplicates are found. Hope this clarifies some things for you. Lachlan -----Original Message----- From: John Mistler [mailto:[EMAIL PROTECTED] Sent: Thursday, 8 July 2004 12:27 PM To: [EMAIL PROTECTED] Subject: Re: INSERT DISTINCT? I am not certain from the documentation whether it is advisable to create a unique multi-column index on two columns that are already individually indexed. The individual indexes I assume I need for when I do a SELECT on those particular columns. The multi-column one I need for the reasons discussed below. Any one know? Thanks, John on 7/7/04 2:21 PM, Joshua J. Kugler at [EMAIL PROTECTED] wrote: > Certainly, it's called making a unique index on the field(s) you want to keep > unique. > > Hope that helps. > > j----- k----- > > On Wednesday 07 July 2004 12:48 pm, John Mistler said something like: >> Is there a way to do an INSERT on a table only if no row already exists >> with the same info for one or more of the columns as the row to be >> inserted? That is, without using a method outside SQL? >> >> Thanks, >> >> John -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
