Instead of ...

[code]
select
a.col1,
(
Select
b.col2
from
b
where
b.col1 = a.col1
) col2
from
a
[\code]

... you would write ...

[code]
select
a.col1,
b.col2
from
a,
b
where
a.col1 = b.col1(+)
[\code]

It ios the "(+)" that makes this an outer join, and causes all rows from a to be returned regardless of whether there is a corresponding value of col1 in table b. If there is no corresponding value, the second column of the query result will be null.