Re: Apparently I don't understand full outer joins....

On Tue, 25 Jan 2005, Ben wrote:

> I run this:
>
> select
> coalesce(a.n,0) as a,
> coalesce(b.n,0) as b,
> coalesce(a.s,b.s) as s
> from
> ( select 1 as n, 0 as s) a full outer join
> ( select 2 as n, 1 as s) b
> on
> a.s = b.s
>
> ... and get this:
>
> a | b | s
> ---+---+---
> 1 | 0 | 0
> 0 | 2 | 1
> (2 rows)
>
>
> Perfect! Now, I try to extend my understanding to 3 subselects:
>
> select
> coalesce(a.n,0) as a,
> coalesce(b.n,0) as b,
> coalesce(c.n,0) as c,
> coalesce(a.s,b.s,c.s) as s
> from
> ( select 1 as n, 0 as s) a full outer join
> ( select 1 as n, 1 as s) b full outer join
> ( select 2 as n, 2 as s) c
> on
> a.s = b.s and
> b.s = c.s
>
>
> .... and get a syntax error at the end of my query. Apparently what I'm
> trying to do doesn't make sense?

Each outer join gets an on clause. You might want something like:
select
coalesce(a.n,0) as a,
coalesce(b.n,0) as b,
coalesce(c.n,0) as c,
coalesce(a.s,b.s,c.s) as s
from
( select 1 as n, 0 as s) a full outer join
( select 1 as n, 1 as s) b on (a.s=b.s) full outer join
( select 2 as n, 2 as s) c on b.s = c.s;