>>> "Marc Rohloff" <Marc.Rohloff@eskom.co.za> 01.11.2000 09.02 Uhr >>>
>
> select a.col1, b.col2 from a,b
> where a.col1 = b.col2
> or b.col2 is null
>
This query has nothing to do with an outer join. See the following example:
table a
c1
---
x
y
and
table b
c2
---
x
Then an outer join gives:
select a,c1, b.c2
from a left outer join b on a.c1 = b.c2
c1 | c2
x | x
y | (null)
but your query gives:
select a.c1, b.c2
from a, b
where a.c1 = b.c2 or b.c2 is null
c1 | c2
x | x
because there are no rows in table b with c2 is null
-------------
Gerhard
