#使用if(条件,结果1,反之结果) select id,name,grade_num from( select user_id id,name,t.grade_num grade_num,rank()over(order by grade_num desc)num from user u left join (select user_id,sum(if(type = "add",grade_num,-1*grade_num)) grade_num from grade_info group by user_i...