> Not every DBMS... > > MSSQL: > Create Unique Index > Microsoft(r) SQL Server(tm) checks for duplicate values when the index > is created (if data already exists) and checks each time data is added > with an INSERT or UPDATE statement. If duplicate key values exist, the > CREATE INDEX statement is canceled and an error message giving the first > duplicate is returned. Multiple NULL values are considered duplicates > when UNIQUE index is created. > > > SYBASE: > Create Unique Index > Prohibits duplicate index (also called key) values. The system checks > for duplicate key values when the index is created (if data already > exists), and checks each time data is added with an insert or update. If > there is a duplicate key value or if more than one row contains a null > value, the command is aborted and an error message giving the duplicate > is printed.
An unique index is not a primary key constraint. With regards, Martijn Tonies Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL Server Upscene Productions http://www.upscene.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
