How do I apply the following constraint/rule?
If I have the following relation R1(a1, a2) and I want to enforce a rule where when a tuple in R1 is created the
attribute a2 can not ever be updated (after it's been given it's initial value by the insert of the tuple).
So basically a2 is not changable after it's created.
How is this done in postgresql?
Thanks
Rob
