>Can I set multiple columns as primary key in mysql so that it is the >COMBINATION that is unique? hi peter according to the manual, yes, you can "A PRIMARY KEY can be a multiple-column index. However, you cannot create a multiple-column index using the PRIMARY KEY key attibute in a column specification. Doing so will mark only that single column as primary. You must use the PRIMARY KEY (index_col_name, ...) syntax." http://mysql.com/Manual_chapter/manual_Reference.html#CREATE_TABLE rudy r937.com