There is one row in the SYSGROUP system view for each member of each group. This view describes the many-to-many relationship between groups and members. A group may have many members, and a user may be a member of many groups.

 Constraints on underlying system table

PRIMARY KEY (group_id, group_member)

FOREIGN KEY group_id (group_id) REFERENCES SYS.ISYSUSER (user_id)

FOREIGN KEY group_member (group_member) REFERENCES SYS.ISYSUSER (user_id)