Assign "Access level" for document in PhPMyadmin

Hi,

I have just migrated my DOCman from 1.6 to 2.0.

I have different document permission under a "Public" Category, hence, i can't use the "Inherit from category" and i need to reassign permission to each "Document" rather to "Category".

Instead to modify the permission for 200+ document on the web interface, i decided to modify it in PhPMyadmin. I have created the user groups and i can see these value under "prefix_usergroups" table, now i need to assign these group to the document.

Can you please tell me what {column} in what {table} i should modify to change the permission for document?

Thank you.