Join switched automatically!

[Grace]

Can anyone tell me what would cause a join to switch from
an outer join to an inner join automatically? I had a
query that somehow changed without me even touching the
query!! Very strange.

Just thought I'd ask.

Thanks, Grace

 

[Michel Walsh]

Hi,


The behavior of the outer join can be reduced to the one of an inner
through testing not appropriately for the NULL that can generate the outer
join.



SELECT whatever
FROM a LEFT JOIN b ON a.f1=b.f2
WHERE b.City= 'Iqaluit'




would produce exactly the same result as if you used an INNER JOIN. Indeed,
any NULL produced by the LEFT JOIN in table b would be discarded further on,
since none of they would be equal to Iqaluit.



Hoping it may help,
Vanderghast, Access MVP