Suppose I have an index on 5 columns (A, B, C, D, E).
If my WHERE clause is not in that order, will the optimizer reorder
them as necessary and possible?
WHERE A=1 AND C=3 AND B=2 AND E=5 AND D=4
Obviously it can't reorder them in all cases:
WHERE A=1 AND (C=3 OR B=2) AND (E=5 OR D=4)
If I don't specify columns in the WHERE clause, how much can it use
the index? I think it is smart enough to use beginning columns:
WHERE A=1 AND B=2
How about skipping leading columns?
WHERE B=2
How about skipping intermediate columns?
WHERE A=1 AND C=3
Or both, which is probably the same?
WHERE B=2 AND D=4?
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Felix Finch: scarecrow repairman & rocket surgeon / felix@crowfix.com
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