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Re: MERGE as the imperative form of aggregation

From: paul c <toledobythesea_at_oohay.ac>
Date: Sun, 08 Apr 2007 15:54:15 GMT
Message-ID: <He8Sh.44940$DE1.43503@pd7urf2no>


Marshall wrote:
> ...
> So, what else has a transform that has a concept of
> identity and also specifies a key? An aggregate
> with GROUP BY.
>
> MERGE NewFooCount f' into FooCount f
> GROUP BY id
> SET f.count = sum(f.count, f'.count);
>
> It's less general, but syntactically and conceptually
> cleaner and simpler.
> ...

I'd say MERGE is still a bastard because it operates on tuples, not relations, ie., a tuple in one operand is not necessarily in the result, whereas UNION, say, isn't like that. It appears to be using a label to hide the real construction, eg., "UPDATE OR INSERT".

p Received on Sun Apr 08 2007 - 10:54:15 CDT

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