How to get a count even if there are no results corresponding mysql?

Question

I am formalating a query to give the number of reports submitted over the last year ordered by date. I get the current year and month with php:

$year = date         


        

Answer 1

count(col_name) AS count will give you count 0

For reference you can visit http://www.mysqlperformanceblog.com/2007/04/10/count-vs-countcol/

Answer 2

You should LEFT JOIN this table with 1..12 table. Something like this:

SELECT  Months.id AS `month` ,
COUNT(`reports`.date_lm) AS `count`
FROM 
(
  SELECT 1 as ID UNION SELECT 2 as ID UNION  SELECT 3 as ID UNION SELECT 4 as ID 
  UNION  
  SELECT 5 as ID UNION SELECT 6 as ID UNION SELECT 7 as ID UNION SELECT 8 as ID 
  UNION  
  SELECT 9 as ID UNION SELECT 10 as ID UNION SELECT 11 as ID UNION SELECT 12 as ID
) as Months
LEFT JOIN `reports` on Months.id=month(`reports`.date_lm)
                       AND 
                       (status = 'submitted') 
                       AND (date_lm > 2012-08)
GROUP BY Months.id 
ORDER BY Months.id ASC

SQL Fiddle demo

Answer 3

Hope this can help..

SELECT
    t1.month_year AS month,
    COALESCE(SUM(t1.total+t2.total), 0) AS count
FROM
(
  SELECT 
  DATE_FORMAT(a.Date, "%Y-%m") AS md,
    DATE_FORMAT(a.Date, "%b-%y") AS month_year,
  '0' AS  total
  FROM (
    SELECT curdate() - INTERVAL (a.a + (10 * b.a) + (100 * c.a)) DAY AS Date
    FROM (SELECT 0 AS a UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS a
    CROSS JOIN (SELECT 0 AS a UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS b
    CROSS JOIN (SELECT 0 AS a UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS c
  ) a
  WHERE a.Date <= NOW() AND a.Date >= Date_add(Now(),INTERVAL - 11 MONTH)
  GROUP BY md
)t1
LEFT JOIN
(
  SELECT DATE_FORMAT(created_at, "%b") AS month, COUNT(*) AS total ,DATE_FORMAT(created_at, "%Y-%m") AS md
  FROM reports
  WHERE created_at <= NOW() AND created_at >= Date_add(Now(),INTERVAL - 11 MONTH) AND `status` = 1
  GROUP BY md
)t2 
ON t2.md = t1.md
LEFT JOIN
(
  SELECT DATE_FORMAT(date_lm, "%b") AS month, COUNT(*) AS total ,DATE_FORMAT(date_lm, "%Y-%m") AS md
  FROM tbl_users 
  WHERE date_lm <= NOW() AND date_lm >= Date_add(Now(),INTERVAL - 11 MONTH) AND status = 'submitted'
  GROUP BY md
)t3 
ON t3.md = t1.md 
GROUP BY t1.md
ORDER BY t1.md

this will give data for last 12 months even if there is no data for it with a 0..

Answer 4

In order to do this, you could create a 'month' table and then use a left outer join between that table and the reports table.

I've never used mysql so apologies if the syntax is slightly off, but this would be the query:

SELECT months.monthNumber,
    count(reports.id) AS `count`
FROM `months` left outer join `reports` on months.monthNumber = month(reports.date_lm) 
WHERE (status = 'submitted') 
AND (date_lm > 2012-08) 
GROUP BY monthNumber
ORDER BY monthNumber ASC

Importantly, the count should be of a column in the reports table, not the months table, or else you would never get a zero.