Question

I have the following table named staff_status with structure and records:

----------------------------------------------------
| id (INT) | status (VARCHAR) | status_date (DATE) |
----------------------------------------------------
|   1      |     Working      |    2009-05-03      |
|   2      |     Working      |    2009-07-21      |
|   1      |     Leave        |    2010-02-01      |
|   1      |     Working      |    2010-02-15      |
----------------------------------------------------

Now I want to query this to get the status of the staff on a specific date. Example: status of id = 1 on 2010-02-10 should return Leave while on 2010-03-01 should return Working

What I have tried without success:

SELECT t1.status FROM staff_status t1 INNER JOIN (SELECT * FROM staff_status WHERE id = 1 AND status_date < '2010-02-10') t2 ON (t1.id = t2.id AND t1.status_date < t2.status_date);

Answer 1

You could try something like

SELECT  s.*
FROM    staff_status s INNER JOIN
        (
            SELECT  id,
                    MAX(status_date) status_date
            FROM    staff_status
            WHERE   status_date < '2010-02-10'
            AND     id = 1
        ) m ON  s.id = m.id
            AND s.status_date = m.status_date

Additionaly you could try an ORDER BY status_date DESC LIMIT 1

from 13.2.8. SELECT Syntax

Something like

SELECT  *
FROM    staff_status
WHERE   id = 1
AND     status_date < '2010-02-10'
ORDER BY    status_date DESC
LIMIT 1