I'm working on a CMS, one of the features of the CMS in question is that only one user can edit an item at any given time. I've implemented this by having one table that holds the items, and another table that holds locks. A lock row consists of the ID of the item locked, a timestamp indicating when the item was locked, an interval indicating when the locks expires and a string that holds a reason for the item currently being locked. I want to be able to restrict any query that updates or deletes from the articles table so that they can only occur if there isn't a corresponding entry in the locks table. As far as I can tell, however, you can't join tables when doing updates or deletes. I know on the PHP side I can attempt to do a select on the locks table and only perform the delete if the select returns 0 rows, but I'd rather the update or delete query itself does the checking. Can anyone help out?
