I am trying to set up a database that seems cut out for an SQL "DOMAIN" -- fields that have a restricted syntax for validity and occur in several tables. So, I set the database up and all the CREATE WHATEVER commands appear to work. But, if I try entering any actual data into the tables I get rejected because some type -- generally named like the domain but cased differently or with '_' chars added -- doesn't exist.

Obviously, I'm missing some critical aspect of DOMAINS! Casting functions seems likely, but mine would all be just an assign.

Has anyone actually used domains or user-defined types?

Has anyone even seen a decent tutorial or explanation of the durned things?