Notification data?

[Saintless]

Hi Experts
Can any one help me about from where notification data comes specially in 'Social Group Join Request' link if the group is private. i need to know which is the table and column field name.

For test I find in the 'socialgroup member' table and update manually to fled 'type' from 'moderated' to 'member' and also in 'social group' table field-> 'moderatedmembers' from 1 to 0 and increase 'members' from, current value +1, but notification is not removing. That mean 'Social Group Join Request' link gathering data from other table or table column for notification purpose.

What is that table name and column name where pending notice is storing and after accept it is removing also?

Actually with the default system's 'Pending member Acceptance' i have also a customize section from where i want to accept 'pending member'. it is working fine but only notification is not removing.

Please any one help