The uniqueness constraint would only be enforced during an INSERT or an UPDATE. If your table is read-only, declaring the index as UNIQUE will be overkill. I can't tell you about any kind of performance hit during reading but I try to follow the maxim "don't ask for it if you won't need it". I would use just a straight index.
Shawn Green Database Administrator Unimin Corporation - Spruce Pine Wesley Furgiuele <[EMAIL PROTECTED]> wrote on 09/09/2004 04:36:50 PM: > Hi: > > I was wondering if there is any performance-related reason to use a > unique index versus a standard index? Is the only benefit of a unique > index that it will prevent duplicate values from being inserted into a > table unless explicitly allowed? > > I have a column, colA, that I know contains only unique values because > I create the table using a 'GROUP BY colA' clause. Before I use the > table for any more work, I want to index colA. This table will have no > further rows added to it, so I don't need to worry about a potential > duplicate value being inserted. I was just wondering if it was a > performance gain/hit to use a unique index, or if the difference was > negligible. > > Thanks. > > Wes > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] >
