How could i alter this Query

Question

SELECT * FROM (
      SELECT t1.eventId,t1.start_date,t1.end_date, COUNT(*) pos FROM events t1
        LEFT JOIN events t2 ON t1.start_date = t2.start_date AND t1.eventId <= t2.eventId
        WHERE t1.start_date BETWEEN  '2012-12-18' AND '2012-12-24'
      GROUP BY
        t1.eventId,t1.start_date
      ORDER BY 
        t1.start_date,pos ASC
      ) t
    WHERE
      pos <= 3;

WHY start date 2012-12-21 and 2012-12-24 does not exist,

if start_date does not exist then, i need a null or empty value for

NOTE : no record for 21 and 24.. in my DB but i need a empty value in my query

Answer 1

Please use below query and tell me the result

SELECT * FROM (
      SELECT t1.eventId,t1.start_date,t1.end_date, COUNT(*) pos FROM events t1
        LEFT JOIN events t2 ON t1.start_date = t2.start_date AND t1.eventId <= t2.eventId
        WHERE t1.start_date >=  '2012-12-18' AND  t1.start_date <='2012-12-24'
      GROUP BY
        t1.eventId,t1.start_date
      ORDER BY 
        t1.start_date,pos ASC
      ) t
    WHERE
      pos <= 3;

Answer 2

You can eliminate the outer query with a HAVING instead:

SELECT t1.eventId,t1.start_date,t1.end_date, COUNT(*) pos FROM events t1
LEFT JOIN events t2 ON t1.start_date = t2.start_date AND t1.eventId <= t2.eventId
WHERE t1.start_date BETWEEN  '2012-12-18' AND '2012-12-24'
GROUP BY t1.eventId,t1.start_date
HAVING COUNT(*) <= 3
ORDER BY t1.start_date,pos ASC;

Note the insertion of this line:

HAVING COUNT(*) <= 3

Which is logically equivalent to what your outer query is doing