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.
