Question

I need to get a list of IDs and a corresponding field from a table where the ID may not exist. For example, the table looks like:

 id  | status
-------------
1234 | A
4567 | B
1020 | C

I want to get the status from rows with id=4567 and id=7777, like this:

Result:
 id  | status
-------------
4567 | B
7777 | 

Since there is no record with id=7777 it should show an empty status field.

What I have so far: I can get an empty row when there is no record for any of the ID matches by joining the result with DUAL. For example:

SELECT id, status FROM DUAL LEFT OUTER JOIN mytable ON id='7777'

Gives the result of an empty row:

 id  | status
-------------
     | 

But adding a valid id to the condition only returns one row:

SELECT id, status FROM mytable WHERE (id='7777' OR id='4567')

 id  | status
-------------
4567 | B

How can I make the query return a row with the requested ID even if it has no record?

Answer 1

SELECT  q.id, m.status
FROM    (
        SELECT  4567 AS id
        FROM    dual
        UNION ALL
        SELECT  7777 AS id
        FROM    dual
        ) q
LEFT JOIN
        mytable m
ON      m.id = q.id