Returning null for joined tables when one column non existant

[Madison Kelly <linux@xxxxxxxxxxx>]

Hi all,

  I've got a query that crosses a few tables. For example:

SELECT
     a.foo, b.bar, c.baz
FROM
     aaa a, bbb b, ccc c
WHERE
     a.a_id=b.b_a_id AND a.a_id=c.c_a_id AND a.a_id=1;

  Obviously, if there is no match in 'bbb' or 'ccc' then nothing will 
be returned, even if there is a match in one or both of the other 
tables. Is there a way to say something like 'b.bar OR NULL' to make 
sure that the matching columns with data still show and ones without a 
match return NULL (or some string)?

Thanks!

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