How about: SELECT a.keyfld, a.foo1, b.foo2, c.foo3 FROM a LEFT JOIN b USING(keyfld) LEFT JOIN c USING(keyfld)
Dmitri > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Lane Van Ingen > Sent: Wednesday, August 17, 2005 12:55 PM > To: pgsql-sql@postgresql.org > Subject: [SQL] Is it This Join Condition Do-Able? > > > 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 > The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
