T-SQL 逻辑控制语句 ifelse while casewhen

ifelse,如果逻辑语句有多行,用begin end 包裹

 

use StudentManageDB
go
--查询成绩
declare @cAvg int
select @cAvg=avg(CSharp) from ScoreList 
inner join Students on ScoreList.StudentId=Students.StudentId where ClassId=1
print 'C#平均成绩：'+convert(varchar(20),@cAvg)
--判断成绩
if(@cAvg>=80)  
    print '软件一班成绩优秀！'  
else
    print '软件一班成绩一般！'

while,如果逻辑语句有多行,用begin end 包裹

 

use StudentManageDB
go
print '加分之前的C#成绩：'
select StudentId,CSharp from ScoreList 
declare @CSharp int,@StuId int
while(1=1)
    begin
        select top 1 @CSharp=CSharp,@StuId=StudentId 
                 from ScoreList where CSharp<60
       if (@CSharp<60) 
          update ScoreList set CSharp=CSharp+1 
                where StudentId=@StuId
       if((select count(*) from ScoreList where CSharp<60)=0)
         break
   end
print '加分之后的C#成绩：'
select StudentId,CSharp from ScoreList 

case when

 

use StudentManageDB
go
select 学号=StudentId,
总评=CASE
                when (CSharp+SQLServerDB)/2>=90 then  'A'  
                when (CSharp+SQLServerDB)/2 between 80 and 89 then  'B'  
                when (CSharp+SQLServerDB)/2 between 70 and 79 then  'C'  
                when (CSharp+SQLServerDB)/2 between 60 and 69 then  'D' 
                else '不及格' 
          end
from ScoreList