Re: SQL Gurus ...

On Mar 12, 2021, at 10:18 AM, Darren Strong <darren@xxxxxxxxx> wrote:

Change your "where" to an "and" to make the b.event part of the left outer join and it will work as you're expecting. The "where" is being applied after the join is complete, so, has a different affect.

select count(*)
from table1 a left outer join table2 b
on a.email = b.email
and b.event = '2103SM'
order by attend;

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Subject: SQL Gurus ...

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Can someone please explain how I can ever get a lower row count from a left outer join than the number of rows that exist in the left table?

select count(*)
from table1 a left outer join table2 b
on a.email = b.email
where b.event = '2103SM'
order by attend;

That returns query returns a count of 848 rows. There are 858 rows in table1! (left table). And just for fun an inner join also returns 848 rows.

Any ideas anyone? I thought it was an absolute that a left outer always returned all rows in the left table.


Jon Paris

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