Re: 3 way outer join dilemma

On Mon, 18 Aug 2003 terry@ashtonwoodshomes.com wrote:

> Here's what I have (simplified)
>
> SELECT t1.fid, t1.t1_data, t2.vid, t2.t2_data, t3.t3_data
> FROM t1, t2, t3
> WHERE t1.fid = X
>   AND t2.vid = Y
>   AND t3.fid = t1.fid
>   AND t3.vid = t2.vid
>
> Now, I discover that the record in t3 may not always exist, so somehow I
> want to do an outer join...
>
> SELECT t1.fid, t1.t1_data, t2.vid, t2.t2_data, t3.t3_data
> FROM t1, t2, OUTER JOIN t3 ON (t3.fid = t1.fid AND t3.vid = t2.vid)
> WHERE t1.fid = X
>   AND t2.vid = Y
>
> But I get the statement that "t1 is not part of JOIN"

If t3 may not have a record, then how can you be using it to join t2 ?

It seems that if t3 doesn't exist, then of course "AND t3.vid = t2.vid" is
going to be "AND NULL = t2.vid" which of course, will always be false,
i.e. you'll never be able to join t2.  Is there a common key between t2
and t1?