Peter Lauri wrote:
[snip "Chris"]
The 'where' clause cuts that down to only matching records between the
tables. Without the where, you'd end up with lots of rows but with the
where it will be fine.
[/snip]
Yes, it cuts it down to that number of records in the end, so the final
result set will just be a few rows that match the 'WHERE'. But the internal
process of MySQL do merge all tables and then chooses the records that
matches the 'WHERE' clause.
I don't know enough about mysql internals to debate that so I'll take
your word for it.
'Explain' doesn't give enough information about what happens behind the
scenes so I'm not sure how to prove/disprove that and I don't know of
any tools that would show you that (if there is let me know!).
Having said all of that I've never had a problem doing it the way I
mentioned.. ;)
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