如何将列转换为行或 Vica Versa

Question

我有两张桌子

学生：

         Name       Class  Maths Science English Hindi
         Sonia        2     98     67      53     58
         Vijay        7     89     68      45     51
    Abhishek Mishra   6     87     89      52     53
         Rupal        8     74     76      59     64
         Gaurav       10    90     78      43     41

主题：

Subject  Total_Marks
Maths       100
Science     100
English     75
Hindi       75

当我select命名sonia时，它应该提供以下SQL输出：

Subject Total_Marks Obtained Marks
Maths     100            98
Science   100            67
English    75            53
Hindi      75            58

Answer 1

这有点像学校问题，但如果你怀疑的话，你应该尝试 UNPIVOT 语法而不是 PIVOT 语法。

参见 MSDN 文档以了解两者 here

使用 UNPIVOT 后跟 LEFT JOIN，查询应该如下所示

select UP.Subject,Total_Marks, Obtained_Marks from 
    (   
        select 
            S.Name as Name, 
            S.Maths as Maths, 
            S.Science as Science, 
            S.English as English, 
            S.Hindi as Hindi 
        from Student S
        where S.Name like 'sonia'
    )source
UNPIVOT 
    (
    Obtained_Marks for Subject in (Maths,Science, English, Hindi)
    )UP

LEFT JOIN  Subject S
ON S.Subject=UP.Subject

INSERT 用于架构的查询：

create table subject(subject varchar(10), total_marks int)
insert into subject values('Maths',100),('Science', 100),('English', 75),('Hindi', 75)
create table student(name varchar(100),class int,maths int, science int,english int,hindi int)
insert into student values
('sonia',2,98,67,53,58),
('vijay',7,89,68,45,51)

Answer 2

好吧，不用UNPIVOT也能达到你想要的效果，像这样-

DECLARE @subject table (subject varchar(10), total_marks int)

DECLARE @student table (name varchar(100),class int,maths int, science int,english int,hindi int)


INSERT INTO @subject
    VALUES ('Maths', 100), ('Science', 100), ('English', 75), ('Hindi', 75)


INSERT INTO @student
    VALUES ('sonia', 2, 98, 67, 53, 58),
        ('vijay', 7, 89, 68, 45, 51)


SELECT ri.subject, ri.total_marks, le.val as ObtainedMarks FROM 
(
    SELECT name, class, t.sub, t.val FROM @student
    CROSS APPLY (VALUES ('maths', maths), ('science', science), ('english', english), ('hindi', hindi)) AS t(sub, val)
) le
INNER JOIN
(
    SELECT * FROM @subject
) ri
ON le.sub = ri.subject
WHERE le.name = 'sonia'

这里我使用了 CROSS APPLY 和 VALUES 子句来制作主题名称作为键和它的列值作为值的键值对组合。

结果

subject  total_marks    ObtainedMarks
-------------------------------------
 Maths     100         98
 Science   100         67
 English    75         53
 Hindi      75         58

如何将列转换为行或 Vica Versa

How to convert Columns into Rows or Vica Versa

sql

sql-server

pivot