Hopefully the Tag1 is null or Tag1 = '' solution will work for you, but I'd like to point out that your database design appears to violate first normal form. I'm a pragmatist and realise there's often reasons for violating things that are held to be good design principles, but first normal form is a pretty useful guideline for database design. The Wikipedia article I linked gives a pretty good summary for what first normal form is, why it's a good idea, and how to make your database follow it.