Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

>> I believe that NULLs and duplicates did not result from a mad rush
to get something into the SQL-standard, but were very deliberate and conscious design decisions made in the mid 70's. <<

The person responsible was Dr. E.F. Codd, who had a NULL and PRIMARY KEY in the first version of the Relational Model and amended the model to have two types of NULL (is the attribute there and a value missing, or is the attribute missing completely?).

>> the point is still valid that it will never get removed once
introduced. <<

No. The removal of a language feature is called "deprecation" in the Standards game and it is a [pun] standard procedure. In fact whole standards get removed (GMT, the old IBM flowchart, as a few examples. Is PL/I legally dead yet?). So far, SQL has removed ordinal position numbers for columns as one concrete example. Received on Fri Mar 14 2003 - 18:46:09 CST