Re: Object Class and Data Type

From: Laconic2 <laconic2_at_comcast.net>
Date: Mon, 5 Apr 2004 08:45:02 -0400
Message-ID: <h-KdnYOHZqs1yezdRVn-gw@comcast.com>

DEC RDB supported domains (called global fields) way back in 1983. But it did not prohibit joins across domains. In 1986, when they added support for SQL, they put in a create domain command.

However, it was easy to find joins across domains by a query on the metadata.

I haven't tracked RDB since 2001, so they may have added it.

The reason I ask is that DEC's data dictionary at first made the record the most basic dictionary item. There was a huge debate, and eventually the domain was added as the fundamental lexical entry.

IIRC, Martin wrote on this subject, back in the 1970s.

Now I have two other questions:

First, when did CREATE DOMAIN make it into mainstream SQL? Second, does the relational model have an equivalent concept? I would think it would have to, given the definition of a relation. Received on Mon Apr 05 2004 - 07:45:02 CDT