Question

I have a question about my mysql query.
I want to count the number of records per day.
That works, but I also want to see the dates on which the count is 0.
The dates where the total is 0 is not in the resultset.
How do I do that?
This is my current query:

SELECT COUNT(id) AS total_per_day, 
DATE_FORMAT(reg_date, "%Y-%m-%d") as my_date 
FROM my_table GROUP BY my_date

Thanks in advance for your replies.

Answer 1

Try this query –

-- Create this temp. table firstly!
-- CREATE TABLE days(d int);
-- INSERT INTO days(d) VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9);

SELECT t.day, COUNT(mt.id) total_per_day FROM (
  SELECT
    min_date + INTERVAL t1.d + t2.d * 10 DAY day,
    min_date,
    max_date
  FROM days t1, days t2,
    (SELECT MIN(DATE(reg_date)) min_date, MAX(DATE(reg_date)) max_date FROM my_table) t3
  HAVING day BETWEEN min_date AND max_date) t
  LEFT JOIN my_table mt
    ON t.day = DATE(mt.reg_date)
GROUP BY t.day