where clause on a left outer join - Mailing list pgsql-sql

From Cris Carampa
Subject where clause on a left outer join
Date
Msg-id cirfem$75c$1@floppy.pyrenet.fr
Whole thread Raw
Responses Re: where clause on a left outer join  (Stephan Szabo <sszabo@megazone.bigpanda.com>)
List pgsql-sql
Hello, let's suppose I have the following tables:

create table parent (  parent_id numeric primary key,  parent_data text
) ;

create table stuff (  stuff_id numeric primary key,  parent_id numeric references parent,  stuff_data text
) ;

And the following data:

crisdb=> select * from parent; parent_id | parent_data
-----------+-------------         1 | aaa         2 | bbb         3 | ccc
(3 rows)

crisdb=> select * from stuff; stuff_id | parent_id | staff_data
----------+-----------+------------        1 |         1 | xxx        2 |         1 | yyy        3 |         1 | zzz
(3 rows)

I wish to write a query that returns all rows from "parent" and, beside 
of them, staff data with stuff_id=1 if available, otherwise null.

The following query:

select  par.parent_id,  stu.stuff_data
from  parent par left outer join stuff stu  on (    par.parent_id = stu.parent_id  )
where  stu.stuff_id = 1
;

Gives the following result:
 parent_id | stuff_data
-----------+------------         1 | xxx
(1 row)

But this is not what I want.

The following query:

select  par.parent_id,  stu.stuff_data
from  parent par  left outer join  (    select      *    from      stuff    where      stuff_id = 1  ) stu  on (
par.parent_id= stu.parent_id  )
 
;

Gives the following result:
 parent_id | stuff_data
-----------+------------         1 | xxx         2 |         3 |
(3 rows)

Which is exacly what I want.

I'm wondering whether there is another way to get this result, without 
using the online view.

Thank you. Kind regards,

-- 
Cris Carampa (spamto:cris119@operamail.com)
I got some John Coltrane on the stereo baby make it feel all right
I got some fine wine in the freezer mama I know what you like
I said a man works hard all day he can do what he wants to at night


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