select systemuser.fullname ,role.name, role.modifiedbyname,role.createdbyname from systemuser,role,systemuserroles
where systemuser.systemuserid=systemuserroles.systemuserid and systemuserroles.roleid = role.roleid
-- 下面是用join方式,更加explicit。上面是多表查询方式,更加简洁
select fullname as systemuser_fullname,role.name as role_name,role.modifiedbyname,createdbyname from role
join (
select systemuser.fullname,roleid
from systemuser
join systemuserroles on systemuserroles.systemuserid=systemuser.systemuserid
) as t on role.roleid=t.roleid