Question

I have 2 queries like :

select id, count(something) selected from table1...;
select id, count(something) rejected from table2...;

The first query gives me

id selected
------------
2  4
3  5

The second query gives me

id rejected
------------
1  12
3  13

I wish to combine them into the following form through a single query

id selected rejected
--------------------
1  null      12
2  4         null 
3  5         13

How can I achieve this ?

Answer 1

You need to simulate SQL Server‘s FULL OUTER JOIN by combining the UNIONed results of LEFT and RIGHT joins (but in my case both are LEFT JOIN as I used to to this)

SELECT  a.ID, a.selected, b.rejected
FROM    (selectedQuery) a
        LEFT JOIN (rejectedQuery) b
            ON a.ID = b.ID
UNION 
SELECT  a.ID, b.selected, a.rejected 
FROM    (rejectedQuery) a
        LEFT JOIN (selectedQuery) b
            ON a.ID = b.ID

SQLFiddle Demo

UPDATE 1

PostgreSQL Supports FULL OUTER JOIN (my bad)

SELECT  COALESCE(a.ID,b.id) ID, a.selected, b.rejected
FROM    selectedQuery a
        FULL OUTER JOIN rejectedQuery b
            ON a.ID = b.ID

SQLFiddle Demo