mysql - Group by day of week to show counts -

i have following table:

| id | product | type | data_start | +----+---------+------+------------+ | 3  | phone   | voip | 2015-07-01 | | 5  | phone   | voip | 2012-03-02 | | 6  | phone   | voip | 2015-07-04 | | 7  | phone   | voip | 2012-03-05 | | 8  | phone   | voip | 2012-03-05 | | 8  | phone   | voip | 2012-03-06 | | 8  | phone   | voip | 2012-03-06 | 

i need genenerate report of 7 days sold in past, although day 03.07.2015 , 07.09.2015 day did not sell me bring 0.

| day | count | +-----+-------+ | 1   |   1   | | 2   |   1   | | 3   |   0   | | 4   |   1   | | 5   |   2   | | 6   |   2   | | 7   |   0   | 

they know how can case? 2 dates not system, mentioned report last 7 days want know day not sold