I've got a very large MariaDB (MySQL) table and ran an EXPLAIN on a
GROUP BY query and a separate DISTINCT query on an indexed field. Both
came back the same in terms of optimization. ymmv.
On 2014-04-16 12:21, Richard Kaye wrote:
I was just throwing out some options that came off the top of my head.
There was no real thought put into optimizing beyond general rushmore
rules.
Do you really need the DISTINCT when the GROUP BY is there? My
understanding, at least as far as VFP SQL is concerned, is that
DISTINCT will force a table scan whereas GROUP BY is rushmore
optimizable and will use an available index tag.
And as Uncle Ted would say, none of this theoretical stuff matters.
You have to test with your data to know your stuff is optimized in
your environment. :-)
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