Re: Using the catalogue

From: <>
Date: 16 Nov 2005 08:25:20 -0800
Message-ID: <>

> > all triplets (field name, value, relation), from any relation, such
> > that field name is in {Name, Designation}, field type is String, and
> > field value = "King"

> It seems that two relational operators would be sufficient. One to
> return the catalogue and one to "evaluate" a union based on some
> restriction of a catalogue relvar. A D language assumes an open ended
> set of user-defined operators and types so I don't see why this should
> be forbidden in Tutorial D for example.
> SQL has the catalogue but the "evaluation" part isn't in standard SQL
> AFAIK. However, all SQL products that I'm familiar with implement some
> form of dynamic SQL as an extension - that should be up to the task.

I see.

And the easiest way I envisage to endow a traditional language with the capability is to extend the language with two things

(1) means to create strings by concatenating any part of the result of any query

(2) an interpreter function

I think many SQLs already have (1), and as for (2) clearly the DBMS has an SQL interpreter inside so it is just a matter of making it available in the language (as some programming languages do e.g. Clipper, Snobol).

Ok, so I guess my question is not one of possible vs. impossible anymore but of "how well"---which is a very much harder question to answer altogether, so let me start again:

(a) is this an interesting problem at all?

(b) does it occur in the real world?

Thanks a lot.
--Marius Received on Wed Nov 16 2005 - 17:25:20 CET

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