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Re: Lucid statement of the MV vs RM position?

From: Tony Andrews <andrewst_at_onetel.com>
Date: 24 Apr 2006 10:02:35 -0700
Message-ID: <1145898155.724133.108640@j33g2000cwa.googlegroups.com>


dawn wrote:
> 'The entire information content of a relational database is
> represented in one and only one way: namely, as attribute values within
> tuples within relations.'"

<SNIP>
> Are you suggesting that there have been implementations where list
> attributes have been defined (as UDTs) in such a way that the query
> language understands and properly handles values that are lists
> (ordered)? When defining this type, is it easy enough to implement it
> so that ALL and EVERY (or whatever) will function properly from SQL
> against these lists (not just against RVAs)?

Why would the query language have to understand lists? The whole point of UDTs is that they are User Defined, which means that their implementation and meaning is not known to the query language. The definer of the UDT would define "operators" (aka "methods") to do the things that can be done with values of that UDT, and you could use those operators in your queries. Lists are just one of a squillion UDTs that could be defined, and surely you don't expect the DBMSs built-in query language to "understand" them all? Received on Mon Apr 24 2006 - 12:02:35 CDT

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