The GROUPS and NODEGROUP tables are used to defined pages that specifically combine results for a set of nodes into a results page.
Currently, these must be entered manually into the database by an account with write privileges into the database.
For example the following SQL statement will enter a group in the GROUPS table, and automatically assign it a 'groupid' (say 1):
insert into GROUPS (groupname,comment,active) values ('ULTRALIGHT', 'Ultralight Nodes',1);
The following command will enter a nodeid and its groupid into the NODEGROUP table:
insert into NODEGROUP (groupid, nodeid) values (1, 10);
Node that the 'nodeid' is the 'nodeid' field in the NODES table and 'groupid' is the groupid field in the GROUPS table.