Garrett,
LEFT JOIN b ON a.key = b.key*AND b.field = 'Value'*
is it the conditions/filters (AND b.field = 'Value') that you are asking
about, not the difference between WHERE and JOIN?
If so, then this might help:
https://stackoverflow.com/questions/10517225/filtering-joins-where-vs-on
or this:
https://stackoverflow.com/questions/10297231/where-clause-vs-on-when-using-join
Frank.
Frank Cazabon
On 02/04/2019 06:05 PM, Garrett Fitzgerald wrote:
Hey, all. I had a general SQL question. Often, I find myself needing to use
the syntax:
FROM a
LEFT JOIN b ON a.key = b.key AND b.field = 'Value'
because if I filter b.field in the WHERE clause, I've effectively made the
LEFT JOIN an inner one.
That makes me wonder, at what point do we stop moving conditions to the
JOIN clause? Obviously, some can't move for syntactical reasons, such as
subqueries. But short of that, when does it make sense to limit a non-outer
join in the join criteria? Never?
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