黑马视频-SQL之case

select 
   tscoreId,
   tsid,
   tenglish,
   评级=case
         when tenglish>=95 then ‘优秀‘
         when tenglish>=90 then ‘良好‘
         when tenglish>=80 then ‘中‘
         when tenglish is null then ‘缺考‘
         else ‘以后的比尔盖茨‘
    end
from TblScore

then 后面的数据后类型必须一致

是等值判断
select 
   tscoreId,
   tsid,
   tenglish,
   评级= 
      case tenglish
when 100 then ‘一百分‘
when 90  then ‘九十分‘
            end
from TblScore

相当于switch

Create table Test1(
 A int,
 B int
)

insert into Test1(10,20)
insert into Test1(100,21)
 

select A,B,AOrB=
       case 
          when A>B then A
          else B
       end
from Test1

统计每个销售员的总销售金额，列出销售员名称，总销售金额、称号（>6000金牌；>5500银牌；...）

select

销售员,

销售总金额=sum(销售数量*销售价格),

称号=

case

when sum(销售数量*销售价格)>6000 then ‘金牌销售员‘

when sum(销售数量*销售价格)>5500 then ‘银牌销售员‘

when sum(销售数量*销售价格)>4500 then ‘铜牌销售员‘

else ‘普通销售员‘

end

from Order

group by 销售员

order by 销售总金额 desc

create table Test1(

number varchar(10),

amount int

)

insert into Test(number ,amount) values  (‘RK1‘，10)

insert into Test(number ,amount) values  (‘RK2‘，20)

insert into Test(number ,amount) values  (‘RK3‘，-30)

insert into Test(number ,amount) values  (‘RK4‘，-10)

正数为收入，负数支出

单号|收入|支出

select

number,

收入=

case

when amount>0 then amount

end

来自为知笔记(Wiz)