Question

I’ve got a query:

SELECT
    taskDeadline,
    subtasksDeadline,
    REPLACE(
        LEAST(
            COALESCE(t.deadline, 2147483647),
            COALESCE(sub.deadline, 2147483647)
        ), 2147483647, NULL
    ) AS Deadline
FROM
    tasks t
    LEFT OUTER JOIN subtasks sub ON sub.task_id = t.id

This produces a result like this:

taskDeadline | subtasksDeadline | Deadline
1338501600   | 1333058400       | 1333058400
1334268000   | NULL             | 1334268000
NULL         | 1328050800       | 1328050800
NULL         | NULL             | NULL
1353798000   | 0                | 0
0            | 1353798000       | 0

I’m almost there. I’ve used 2147483647 as the maximum value of the data type (Mysql INT), the only problem I still have, is that if I’ve two values of which one is 0, I want to get the other value. I’ve spend some time but cannot get there. Can somebody shed a light on this?

Answer 1

Or just add NULLIF to your existing COALESCE –

SELECT
    taskDeadline,
    subtasksDeadline,
    NULLIF(
        LEAST(
            COALESCE(NULLIF(t.deadline, 0), 2147483647),
            COALESCE(NULLIF(sub.deadline, 0), 2147483647)
        ), 2147483647
    ) AS Deadline
FROM
    tasks t
    LEFT OUTER JOIN subtasks sub ON sub.task_id = t.id