更新时间:2022-11-27 18:23:40
有两种方法可以执行PIVOT
静态(在其中对值进行硬编码)和动态(在其中执行时确定列).
There are two ways to perform a PIVOT
static where you hard-code the values and dynamic where the columns are determined when you execute.
即使您想要一个动态版本,有时从静态PIVOT
开始然后向动态版本过渡也更容易.
Even though you will want a dynamic version, sometimes it is easier to start with a static PIVOT
and then work towards a dynamic one.
静态版本:
SELECT studentid, name, sex,[C], [C++], [English], [Database], [Math], total, average
from
(
select s1.studentid, name, sex, subjectname, score, total, average
from Score s1
inner join
(
select studentid, sum(score) total, avg(score) average
from score
group by studentid
) s2
on s1.studentid = s2.studentid
) x
pivot
(
min(score)
for subjectname in ([C], [C++], [English], [Database], [Math])
) p
请参见带有演示的SQL小提琴
现在,如果您不知道将要转换的值,则可以为此使用动态SQL:
Now, if you do not know the values that will be transformed then you can use Dynamic SQL for this:
DECLARE @cols AS NVARCHAR(MAX),
@query AS NVARCHAR(MAX)
select @cols = STUFF((SELECT distinct ',' + QUOTENAME(SubjectName)
from Score
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set @query = 'SELECT studentid, name, sex,' + @cols + ', total, average
from
(
select s1.studentid, name, sex, subjectname, score, total, average
from Score s1
inner join
(
select studentid, sum(score) total, avg(score) average
from score
group by studentid
) s2
on s1.studentid = s2.studentid
) x
pivot
(
min(score)
for subjectname in (' + @cols + ')
) p '
execute(@query)
请参见带有演示的SQL提琴
两个版本都会产生相同的结果.
Both versions will yield the same results.
只需四舍五入即可得到答案,如果您没有PIVOT
函数,则可以使用CASE
和聚合函数来获得以下结果:
Just to round out the answer, if you do not have a PIVOT
function, then you can get this result using CASE
and an aggregate function:
select s1.studentid, name, sex,
min(case when subjectname = 'C' then score end) C,
min(case when subjectname = 'C++' then score end) [C++],
min(case when subjectname = 'English' then score end) English,
min(case when subjectname = 'Database' then score end) [Database],
min(case when subjectname = 'Math' then score end) Math,
total, average
from Score s1
inner join
(
select studentid, sum(score) total, avg(score) average
from score
group by studentid
) s2
on s1.studentid = s2.studentid
group by s1.studentid, name, sex, total, average
请参见带有演示的SQL提琴