SQL常用判断语句

1:case when then else end

示例一

SELECT 学号, 姓名, 

 等级= 

    CASE 

    WHEN 总学分 IS NULL THEN ‘尚未选课’

       WHEN 总学分 < 50 THEN ‘不及格’

        WHEN 总学分 >=50 and 总学分<=52 THEN ‘合格’

        ELSE ‘优秀’

    END  FROM  XS    WHERE 专业名=’计算机’

示例二

update employee

set e_wage =

 case

  when job_level = ’1’ then e_wage*1.08

  when job_level = ’2’ then e_wage*1.07

  when job_level = ’3’ then e_wage*1.06

  else e_wage*1.05

 end

示例三

select a, (case a when 1 then '中' else '国' end) AS B  from table1

 

2:isnull()

isnull(sum(incount),0)

 

3:存储过程中执行存储过程

 

  a:直接执行存储过程

　　Exec [sp_OrderGetSendFee] @Cart_ID, 0, @User_ID, @tTotalPrice, @tSendFee, @tSendFee OutPut

  b:执行sql字符串

Set @Str = 'Select @All = Count(*) From ('+ @SQL + ') t'

 Exec sp_ExecuteSQL @Str, N'@All Int OutPut', @TotalRecord OutPut

 

4：执行拼凑sql 语句

 Exec sp_ExecuteSQL @Str

 

5：临时表