delete from system_user_role where user_id=#{userId}
select count(1) from system_user_role where role_id=#{roleId}
delete from system_user_role where user_id in #{userId}
insert into system_user_role(user_id, role_id) values (#{item.userId},#{item.roleId})
delete from system_user_role where user_id=#{userId} and role_id=#{roleId}
delete from system_user_role where role_id=#{roleId} and user_id in #{userId}