How to generate data in MySQL?

Question

Here is my SQL:

SELECT 
  COUNT(id),
  CONCAT(YEAR(created_at), \'-\', MONTH(created_at), \'-\', DAY(created_at))
FROM my_table
GROUP BY YEAR(created_at), MO         


        

Answer 1

Testbed:

create table testbed (id integer, created_at date);
insert into testbed values
       (1, '2012-04-01'),
       (1, '2012-04-30'),
       (2, '2012-04-02'),
       (3, '2012-04-03'),
       (3, '2012-04-04'),
       (4, '2012-04-04');

I also use any_table, which I created artificially like this:

create table any_table (id integer);
insert into any_table values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
insert into any_table select * from any_table; -- repeat this insert 7-8 times

You can use any table in your database that is expected to have more rows then max(created_dt) - min(created_dt) range, at least 365 to cover a year.

Query:

SELECT concat(year(dr._date),'-',month(dr._date),'-',day(dr._date)),
       -- or, instead of concat(), simply: dr._date
       count(id)
  FROM (
        SELECT date_add(r.mindt, INTERVAL @dist day) _date,
               @dist := @dist + 1 AS days_away
          FROM any_table t
          JOIN (SELECT min(created_at) mindt,
                       max(created_at) maxdt,
                       @dist := 0
                  FROM testbed) r
         WHERE date_add(r.mindt, INTERVAL @dist day) <= r.maxdt) dr
  LEFT JOIN testbed tb ON dr._date = tb.created_at
 GROUP BY dr._date;