RT 即是一个用户ID对应的所有权限ID
user表 role表 privilege
--------------------- ------------------ ------------------
userID roleid pid
username rolename name userpwd userid roleid
---------------- ------------------- -------------------
user表 role表 privilege
--------------------- ------------------ ------------------
userID roleid pid
username rolename name userpwd userid roleid
---------------- ------------------- -------------------
(
select roleid from role where userid in
(
select userid from user where username = 'somebody'
)
)
(
select roleid from role where userid =
(
select userid from user where username = 'somebody'
)
)