Given three tables: a, b, c ; each consist of a 'keyfld' and a field called
'foo':
tbl a tbl b tbl c
--------- --------- ---------
a.keyfld b.keyfld c.keyfld
a.foo1 b.foo2 c.foo3
I want to always return all of tbl a; and I want to return b.foo2 and c.foo3
if
they can be joined to based on keyfld.a; I know that it will involve a LEFT
OUTER
JOIN on table a, but have not seen any examples of joins like this on 3 or
more
tables.
select a.keyfld, a.foo1, b.foo2, c.foo3
from a, b, c
where a.keyfld = <some value>
and a.keyfld = b.keyfld
and a.keyfld = c.keyfld;
Results could look like this:
a.keyfld a.foo1 b.foo2 c.foo3
xxxx xxxx xxxx (null)
xxxx xxxx (null) xxxx
xxxx xxxx (null) (null)
xxxx xxxx xxxx xxxx
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
