Left joins

Does anyone know an elegant way of doing a left join like

Table 1
abc 1
def 2
ghi <NULL>

Table 2
1 foo
2 bar
3 duh

I'd like to join those to give me:
abc 1 foo
def 2 bar
ghi <NULL> <NULL>

I can currently only envision a way to do this via a union of several
queries filtering out null and non-null fields, but that gets very
cumbersome when you have lots of fields involved and more than two or
three tables to join.

Any suggestions?

Thanks.

--
Peter Eisentraut
PathWay Computing, Inc.