Обсуждение: Oracle outer join porting question

i'm trying to port an existing application from Oracle8i to PostgreSQL but
i'm having problems understanding a certain outer join query type used in
the application. the query includes a normal outer join between two tables
but also uses outer join syntax to join a table with a constant. here's a
simplified version of the query:

SELECT doc.id,doc.title,sub.user_id,sub.operation FROM document doc, document_subscription sub WHERE 6 = sub.user_id(+)
ANDsub.document_id(+) = doc.id;
 

what does the '6 = sub.user_id(+)' condition exactly do in this query?  
how would this be translated SQL92 join syntax used by PostgreSQL?

i've tried converting it to:

SELECT doc.id,doc.title,sub.user_id,sub.operation FROM document doc LEFT OUTER JOIN document_subscription sub ON
sub.document_id= doc.id WHERE (sub.user_id = 6 OR sub.user_id IS NULL);
 

but this query is missing the rows in the documents table which have a
corresponding document_subscription row with 'not user_id = 6'.

here're also simplified definitions of the two tables used in the query
and some test data:

CREATE TABLE document ( id INTEGER, title VARCHAR(100), PRIMARY KEY(id)
);
CREATE TABLE document_subscription ( document_id INTEGER NOT NULL, user_id INTEGER NOT NULL, operation VARCHAR(10)
);

INSERT INTO document VALUES (1, 'doc1');
INSERT INTO document VALUES (2, 'doc2');
INSERT INTO document VALUES (4, 'doc4');
INSERT INTO document_subscription VALUES (1, 5, 'op1');
INSERT INTO document_subscription VALUES (2, 5, 'op2');
INSERT INTO document_subscription VALUES (2, 6, 'op2');

best regards,
-- aspa                    http://www.kronodoc.fi/

On 15 Jan 2003 at 16:31, Marko Asplund wrote:

> 
> i'm trying to port an existing application from Oracle8i to PostgreSQL but
> i'm having problems understanding a certain outer join query type used in
> the application. the query includes a normal outer join between two tables
> but also uses outer join syntax to join a table with a constant. here's a
> simplified version of the query:
> 
> SELECT doc.id,doc.title,sub.user_id,sub.operation
>   FROM document doc, document_subscription sub
>   WHERE 6 = sub.user_id(+) AND sub.document_id(+) = doc.id;
> 
> what does the '6 = sub.user_id(+)' condition exactly do in this query?  
> how would this be translated SQL92 join syntax used by PostgreSQL?
> 
> i've tried converting it to:
> 
> SELECT doc.id,doc.title,sub.user_id,sub.operation
>   FROM document doc LEFT OUTER JOIN document_subscription sub
>   ON sub.document_id = doc.id
>   WHERE (sub.user_id = 6 OR sub.user_id IS NULL);
> 
> but this query is missing the rows in the documents table which have a
> corresponding document_subscription row with 'not user_id = 6'.

What about this:
SELECT doc.id,doc.title,sub.user_id,sub.operation FROM document doc LEFT OUTER JOIN document_subscription sub ON
sub.document_id= doc.id;
 
id | title | user_id | operation
----+-------+---------+----------- 1 | doc1  |       5 | op1 2 | doc2  |       5 | op2 2 | doc2  |       6 | op2 4 |
doc4 |         |
 
(4 rows)


> 
> here're also simplified definitions of the two tables used in the query
> and some test data:

Thanks for supplying the table and data.  That makes things much 
easier.

-- 
Dan Langille : http://www.langille.org/

> -----Original Message-----
> From: Marko Asplund [mailto:aspa@kronodoc.fi]
> Sent: Wednesday, January 15, 2003 4:31 PM
> To: pgsql-sql@postgresql.org
> Subject: [SQL] Oracle outer join porting question
>
>
>
> i'm trying to port an existing application from Oracle8i to
> PostgreSQL but
> i'm having problems understanding a certain outer join query
> type used in
> the application. the query includes a normal outer join
> between two tables
> but also uses outer join syntax to join a table with a
> constant. here's a
> simplified version of the query:
>
> SELECT doc.id,doc.title,sub.user_id,sub.operation
>   FROM document doc, document_subscription sub
>   WHERE 6 = sub.user_id(+) AND sub.document_id(+) = doc.id;
>
> what does the '6 = sub.user_id(+)' condition exactly do in
> this query?
> how would this be translated SQL92 join syntax used by PostgreSQL?
>
> i've tried converting it to:
>
> SELECT doc.id,doc.title,sub.user_id,sub.operation
>   FROM document doc LEFT OUTER JOIN document_subscription sub
>   ON sub.document_id = doc.id
>   WHERE (sub.user_id = 6 OR sub.user_id IS NULL);
>
> but this query is missing the rows in the documents table which have a
> corresponding document_subscription row with 'not user_id = 6'.
>

Try this:

SELECT doc.id,doc.title,sub.user_id,sub.operation FROM document doc LEFT OUTER JOIN document_subscription sub ON
sub.document_id= doc.id AND sub.user_id = 6;  
 Tambet

On 15 Jan 2003 at 16:40, Tambet Matiisen wrote:

> Try this:
> 
> SELECT doc.id,doc.title,sub.user_id,sub.operation
>   FROM document doc LEFT OUTER JOIN document_subscription sub
>   ON sub.document_id = doc.id AND sub.user_id = 6; 

FWIW:

test=# SELECT doc.id,doc.title,sub.user_id,sub.operation
test-#   FROM document doc LEFT OUTER JOIN document_subscription sub
test-#   ON sub.document_id = doc.id AND sub.user_id = 6;id | title | user_id | operation
----+-------+---------+----------- 1 | doc1  |         | 2 | doc2  |       6 | op2 4 | doc4  |         |
-- 
Dan Langille : http://www.langille.org/

On Wed, 15 Jan 2003, Tambet Matiisen wrote:

> ...
> Try this:
> 
> SELECT doc.id,doc.title,sub.user_id,sub.operation
>   FROM document doc LEFT OUTER JOIN document_subscription sub
>   ON sub.document_id = doc.id AND sub.user_id = 6; 

yes, this query seems to give the same results as the original one.  
thanks!

best regards,
-- aspa                    http://www.kronodoc.fi/