Question

I am using mysql and have a table (Log_Table) storing user login dates, a kind of logging table. I need to find out for how many days in a row a user is logged in or
I need to find out if the user is logged-in everyday in the past 10 days. The thing is that I need to find it in only one SQL select command.
The Log_Table has one user_id:int and one login_date:DATE field

Answer 1

http://sqlfiddle.com/#!2/56437/7

SELECT user_id,
       COUNT( DISTINCT DATE( login_date )) AS days
FROM   Log_Table
WHERE  login_date > DATE_SUB( CURRENT_TIMESTAMP, INTERVAL 3 DAY )
GROUP BY user_id
HAVING days >= 3;