create table info1
(
na nvarchar(10) not null,
p1 int,
p2 int,
p3 int
)
insert into info1
select 'aaa',67, 85,90 union all
select 'bbb',97,78,59 na p1 p2 p3
aaa 67 85 90
bbb 97 78 59就是成绩在60以下为不及格,60-75及格,75-89为良好,90-100为优秀
要求出现
na p1 p2 p3
aaa 及格 良好 优秀
bbb 优秀 良好 不及格
(
na nvarchar(10) not null,
p1 int,
p2 int,
p3 int
)
insert into info1
select 'aaa',67, 85,90 union all
select 'bbb',97,78,59 na p1 p2 p3
aaa 67 85 90
bbb 97 78 59就是成绩在60以下为不及格,60-75及格,75-89为良好,90-100为优秀
要求出现
na p1 p2 p3
aaa 及格 良好 优秀
bbb 优秀 良好 不及格
(
na nvarchar(10) not null,
p1 int,
p2 int,
p3 int
)
insert into info1
select 'aaa',67, 85,90 union all
select 'bbb',97,78,59
go
select
na,
p1 =case when p1 between 60 and 75 then '及格' when p1 between 76 and 89 then '良好'
when p1 between 90 and 100 then '优秀' else '不及格' end,
p2 =case when p2 between 60 and 75 then '及格' when p2 between 76 and 89 then '良好'
when p2 between 90 and 100 then '优秀' else '不及格' end,
p3 =case when p3 between 60 and 75 then '及格' when p3 between 76 and 89 then '良好'
when p3 between 90 and 100 then '优秀' else '不及格' end
from info1
na p1 p2 p3
---------- ------ ------ ------
aaa 及格 良好 优秀
bbb 优秀 良好 不及格
p1=case when p1<'60' then '不及格',
when '60'<=p1<'75' then '及格',
when '75'<p1<='89' then '良好',
else '优秀' end,
p2=case when p1<'60' then '不及格',
when '60'<=p1<'75' then '及格',
when '75'<p1<='89' then '良好',
else '优秀' end,
p3=case when p1<'60' then '不及格',
when '60'<=p1<'75' then '及格',
when '75'<p1<='89' then '良好',
else '优秀' end
from info1
,case when P1>=90 then '优秀' when P1>=75 then '良好' when P1>=60 then '及格' else '不及格' end as P1
,case when P2>=90 then '优秀' when P2>=75 then '良好' when P2>=60 then '及格' else '不及格' end as P2
,case when P3>=90 then '优秀' when P3>=75 then '良好' when P3>=60 then '及格' else '不及格' end as P3
from info1
(
na nvarchar(10) not null,
p1 int,
p2 int,
p3 int
)
insert into info1
select 'aaa',67, 85,90 union all
select 'bbb',97,78,59 na p1 p2 p3
aaa 67 85 90
bbb 97 78 59
select a.na,p1=case
when p1 between 60 and 75 then '及格'
when p1 between 75 and 89 then '及格'
when p1 between 90 and 100 then '优秀'
else '不及格'
end,
p2=case
when p2 between 60 and 75 then '及格'
when p2 between 75 and 89 then '及格'
when p2 between 90 and 100 then '优秀'
else '不及格'
end,
p3=case
when p3 between 60 and 75 then '及格'
when p3 between 75 and 89 then '及格'
when p3 between 90 and 100 then '优秀'
else '不及格'
end
from info1 A
/*
na p1 p2 p3
aaa 及格 及格 优秀
bbb 优秀 及格 不及格
*/
SQL CASE WHEN用法
SQL CASE WHEN用法
CASE 可能是 SQL 中被误用最多的关键字之一。虽然你可能以前用过这个关键字来创建字段,但是它还具有更多用法。例如,你可以在 WHERE 子句中使用 CASE 。
首先让我们看一下 CASE 的语法。在一般的 SELECT 中,其语法如下:
SELECT <</SPAN>myColumnSpec > =
CASE
WHEN <</SPAN>A > THEN <</SPAN>somethingA >
WHEN <</SPAN>B > THEN <</SPAN>somethingB >
ELSE <</SPAN>somethingE >
END
在上面的代码中需要用具体的参数代替尖括号中的内容。下面是一个简单的例子:
USE pubs
GO
SELECT
Title,
' Price Range ' =
CASE
WHEN price IS NULL THEN ' Unpriced '
WHEN price <</SPAN> 10 THEN ' Bargain '
WHEN price BETWEEN 10 and 20 THEN ' Average '
ELSE ' Gift to impress relatives '
END
FROM titles
ORDER BY price
GO
这是 CASE 的典型用法,但是使用 CASE 其实可以做更多的事情。比方说下面的 GROUP BY 子句中的 CASE :
SELECT ' Number of Titles ' , Count ( * )
FROM titles
GROUP BY
CASE
WHEN price IS NULL THEN ' Unpriced '
WHEN price <</SPAN> 10 THEN ' Bargain '
WHEN price BETWEEN 10 and 20 THEN ' Average '
ELSE ' Gift to impress relatives '
END
GO
你甚至还可以组合这些选项,添加一个 ORDER BY 子句,如下所示:
USE pubs
GO
SELECT
CASE
WHEN price IS NULL THEN ' Unpriced '
WHEN price <</SPAN> 10 THEN ' Bargain '
WHEN price BETWEEN 10 and 20 THEN ' Average '
ELSE ' Gift to impress relatives '
END AS Range,
Title
FROM titles
GROUP BY
CASE
WHEN price IS NULL THEN ' Unpriced '
WHEN price <</SPAN> 10 THEN ' Bargain '
WHEN price BETWEEN 10 and 20 THEN ' Average '
ELSE ' Gift to impress relatives '
END ,
Title
ORDER BY
CASE
WHEN price IS NULL THEN ' Unpriced '
WHEN price <</SPAN> 10 THEN ' Bargain '
WHEN price BETWEEN 10 and 20 THEN ' Average '
ELSE ' Gift to impress relatives '
END ,
Title
GO
注意,为了在 GROUP BY 块中使用 CASE ,查询语句需要在 GROUP BY 块中重复 SELECT 块中的 CASE 块。
除了选择自定义字段之外,在很多情况下 CASE 都非常有用。再深入一步,你还可以得到你以前认为不可能得到的分组排序结果集。