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Hi all
I am using 9.4.4 on Fedora 22.
I am experimenting with optimising a SQL statement. One version uses 4 LEFT
JOIN’s and a 5-way CASE statement in the body. The second moves the filtering
into the JOIN section, and I end up with 16 LEFT JOIN’s and no CASE
statements.
My test involves selecting a single row. Both versions work. The first
version takes 0.06 seconds. The second takes 0.23 seconds. On further
experimentation, the time for the second one seems to taken in setting up the
joins, because if I omit selecting anything from the joined tables, it still
takes 0.23 seconds.
Exactly the same exercise on Sql Server results in 0.06 seconds for both
versions.
I realise that, if I was selecting a large number of rows, 0.23 seconds is
trivial and the overall result could be different. But still, it seems
odd.
Is this normal, or should I investigate further?
Frank Millman
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