Count where not defined

I have two tables

Notifications Notifications_seen

if notifcation is seen a row is added to notification_seen

But I need to count how many notifcations that's not seen. How do I do this? Any suggestions ?

But how? Where not exist ?

Hmmm why not just have column for that in the notifications table and remove the second table? Isseen(tinyint) or seenat (timestamp) ?

If you really want to have two tables look here.

edited Mar '17

Hmmm why not just have column for that in the notifications table and remove the second table? Isseen(tinyint) or seenat (timestamp) ?

If you really want to have two tables look here.

I think it's the best option.

is_seen -> default value is 0, when seen it's become 1.

So every seen -> count all where is_seen = 1

every unseen -> count all where is_seen = 0