Hi I'm a little new to constraints and am just wonder if it possilbe and how to write a constraint that will not allow a record to be saved if att x is left null if att y is not left null. so if a person compelteds field say for his fore name it forces them to complete the fields for thier sur name also, but it ok to leave both blank.
That would be a CHECK constraint. Have a look in Books Online, have a go, and post if you get stuck.
Out of curiosity - if your data entry person has a "customer" called Mr Smith, you really want them to enter nothing?