Question

What I have are two tables:

mark_notifications

mark_notifications_options

The mark_notifications table contains rows of data that include a column tid and userid

The mark_notifications_options table contains a special column grouptogether

What I am trying to achieve is that if the userid’s mark_notifications_options.grouptogether value is set to 0, it will add up every row that matches his userid in the mark_notifications table

However, if the userid’s mark_notifications_options.grouptogether value is set to 1, it will add up every row that matches his userid where all the tids are grouped, so that if there no matter how many times the same tid value comes up, it only gets counted as 1. I also would like to count the times tid = 0 as a separate entitiy (but NOT grouped) and then I would just add the values later in php.

This is what I have come up with so far, but the resulting values dont make any sense at all, im getting results that number in the thousands (when it should be a low number like 8 for example).

SELECT 
         mark_notifications_options.grouptogether,
         COUNT(mark_notifications.threadid) AS ungrouped, 
         SUM(mark_notifications.threadid = 0) AS total_zero, 
         COUNT(DISTINCT mark_notifications.threadid) AS grouped 
    FROM mark_notifications, mark_notifications_options
   WHERE mark_notifications.userid = $userid
GROUP BY mark_notifications_options.grouptogether

Thanks!!!

Answer 1

You were missing a join predicate, and so were getting the cartesian product (ie resulting in n x n rows).
Try this:

SELECT 
         mark_notifications_options.grouptogether,
         COUNT(mark_notifications.threadid) AS ungrouped, 
         SUM(mark_notifications.threadid = 0) AS total_zero, 
         COUNT(DISTINCT mark_notifications.threadid) AS grouped 
    FROM mark_notifications mark_notifications
    LEFT JOIN mark_notifications_options mark_notifications_options on mark_notifications_options.userid = mark_notifications.userid
   WHERE mark_notifications.userid = $userid
GROUP BY mark_notifications_options.grouptogether