sravis sravis - 2 months ago 15
MySQL Question

MySql count() to return 0 if no records found

I have a set of posts on monthly basis. Now i need an array which contains total records of posts posted in each month. I tried below MySql query, Its working fine, but I was expecting 0(Zero) for months where there is no records. Here its not returning 0.

I read that COUNT() will not return '0', So how do i achieve this?

I tried IFNULL(), and COALESCE() but still getting the same result. Please help with this query. Thank You......

SELECT
count(id) as totalRec
FROM ('post')
WHERE year(date) = '2013'
AND monthname(date) IN ('January', 'February', 'March')
GROUP BY year(date)-month(date)
ORDER BY 'date' ASC


Got Result:

+----------+
| totalRec |
+----------+
| 7 |
| 9 |
+----------+


Expected Result (Where there is no posts for January):

+----------+
| totalRec |
+----------+
| 0 |
| 7 |
| 9 |
+----------+


Sample Data:

+----+---------------------+
| id | date |
+----+---------------------+
| 24 | 2012-12-16 16:29:56 |
| 1 | 2013-02-25 14:57:09 |
| 2 | 2013-02-25 14:59:37 |
| 4 | 2013-02-25 15:12:44 |
| 5 | 2013-02-25 15:14:18 |
| 7 | 2013-02-26 11:31:31 |
| 8 | 2013-02-26 11:31:59 |
| 10 | 2013-02-26 11:34:47 |
| 14 | 2013-03-04 04:39:02 |
| 15 | 2013-03-04 05:44:44 |
| 16 | 2013-03-04 05:48:29 |
| 19 | 2013-03-07 15:22:34 |
| 20 | 2013-03-15 12:24:43 |
| 21 | 2013-03-16 16:27:43 |
| 22 | 2013-03-16 16:29:28 |
| 23 | 2013-03-16 16:29:56 |
| 11 | 2013-03-17 11:35:12 |
+----+---------------------+

Answer

There is no record for the month of January that is why you are getting no result. One solution that works is by joining a subquery with contains list of months that you want to be shown on the list.

SELECT count(b.id) as totalRec
FROM   (
            SELECT 'January' mnth
            UNION ALL
            SELECT 'February' mnth
            UNION ALL
            SELECT 'March' mnth
        ) a
        LEFT JOIN post b
            ON a.mnth = DATE_FORMAT(b.date, '%M') AND
               year(b.date) =  '2013' AND 
               DATE_FORMAT(b.date, '%M') IN ('January', 'February', 'March') 
GROUP  BY year(b.date)-month(b.date) 
ORDER  BY b.date ASC

OUTPUT

╔══════════╗
║ TOTALREC ║
╠══════════╣
║        0 ║
║        7 ║
║        9 ║
╚══════════╝