How do I limit the number of rows returned by this LEFT JOIN to one?

Question

So I think I\'ve seen a solution to this however they are all very complicated queries. I\'m in oracle 11g for reference.

What I have is a simple one to many join w

Answer 1

In Oracle, if you want 1 result, you can use the ROWNUM statement to get the first N values of a query e.g.:

SELECT *
FROM TABLEX
WHERE
ROWNUM = 1 --gets the first value of the result

The problem with this single query is that Oracle never returns the data in the same order. So, you must oder your data before use rownum:

SELECT *
FROM
    (SELECT * FROM TABLEX ORDER BY COL1)
WHERE
ROWNUM = 1

For your case, looks like you only need 1 result, so your query should look like:

SELECT *
FROM
    TABLE1 T1
    LEFT JOIN 
    (SELECT *
    FROM TABLE2 T2 WHERE T1.ASSIGNMENT = T2.ASSIGNMENT_GROUP
    AND
    ROWNUM = 1) T3 ON T1.ASSIGNMENT = T3.ASSIGNMENT_GROUP