1.简化客户端
2.计算在服务器端进行
六.select 出版社 from Table where 类=business
七.select case when scores>=90 then '优' when scores<90 and scores>=80 then '良' when scores<80 and scores>=70 then '中' when scores<70 and scores>=60 then '及格' when scores<60 then '不及格' else '无成绩' end as '成绩' from Table