Hi, > I want to do this: > > [1] read a row from table table_1 with select > [2] change a row from [1] with update > [3] change another row in table table_1 with update > > But queries [2] and [3] in the time of invoking, assume that row from query > [1] wasn't changed. > > Should I use LOCK TABLES? - I've tried that in query browser, but that > doesn't prevent another thread to modify locked table.
One of the easiest ways is to start a read consistent transaction, read the values for the rows you want to update. Next, update the rows, but not just include the primary key to locate the row, but also use the values you want to modify. eg: I want to update a customer record and change his address. <read address info> update customer set address = 'New Address' where customer_id = 121 and address = 'Old Address' If this update fails to locate rows, you know that someone else changed the value in the Address field before you were able to update it. Martijn Tonies Database Workbench - tool for InterBase, Firebird, MySQL, NexusDB, Oracle & MS SQL Server Upscene Productions http://www.upscene.com My thoughts: http://blog.upscene.com/martijn/ Database development questions? Check the forum! http://www.databasedevelopmentforum.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
