MySQL: group by consecutive days and count groups

Question

I have a database table which holds each user\'s checkins in cities. I need to know how many days a user has been in a city, and then, how many visits a user has made to a c

Answer 1

for a first sub-task:

select count(*) 
from (
select TO_DAYS(p.d)
from p
group by TO_DAYS(p.d)
) t