In article <[EMAIL PROTECTED]>, [EMAIL PROTECTED] writes: >> Keith, >> Your method won't guarantee that there are no rows where the combination >> of the values in those four columns fails to repeat in any other row. To >> do that would require an EXTRA four-column unique index of type UNIQUE. >> Your proposal would actually make the situation worse as now there would >> be two indexes to maintain to achieve the same effect as the previous >> single PK.
> Thankyou for your expert reply Shawn. > Is it not possible to mark each of those those column values > as UNIQUE without them becoming a part of the index as > well? Or is this a contradiction in terms? In theory it would be possible to add a uniqueness constraint to a column without an index, but this would cause a full table scan on every INSERT. AFAIK therefore MySQL automatically puts an index on this column. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
