A Domain for Data

Voice of the DBA

A domain is a set of possible values (among other definitions). I use this word a lot in my work, often with a problem domain (the thing you're trying to solve) or the domain of possible values (like the US States and Territories list). That last one is interesting, as this is often the set of data we stick in some reference or lookup table to use in a form on a screen.

There is a domain as part of the SQL specification, which I never knew about. I was reading an article from Joe Celko on the CREATE DOMAIN statement. This doesn't exist in SQL Server and T-SQL, but it has been a part of PostgreSQL for quite a few versions. The article talks about the definition of a domain from a few very experienced database design people.

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