Re: Q on views and performance

On 2008-02-23 08:21, Kynn Jones wrote:
> ...
>
> 3. Why not write:
>
> CREATE VIEW txt AS
> SELECT a1.word AS word1, a1.type AS type1, a2.word AS word2,
> a2.type AS type2
> FROM T a1 [LEFT] JOIN T a2 USING( zipk ); -- Use "LEFT" if
> appropriate
> SELECT word1, word1
> FROM S JOIN txt ON word = word1
> WHERE type1 = <int1> AND type2 = <int2>;
>
>
> This is would indeed produce the same results as Q1, but this approach
> would require defining about 10,000 views, one for each possible pair
> of int1 and int2

Why 10,000 views??? What's wrong with the ONE view above? You DON'T
want to be defining VIEWs based on actual tables VALUES; leave that to
the SELECT. For that matter, what's wrong with the final SELECT I
listed (below)?

SELECT a1.word AS word1, a2.word AS word2
FROM S JOIN T a1 USING( word )
LEFT JOIN T a2 USING( zipk )
WHERE a1.type = <int1> AND a2.type = <int2>;

-- Dean

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