SQL Server行列相互转换的方法详解

create table test1(
	id int identity(1,1) not null,
	name varchar(255) null,
	course varchar(255) null,
	score int null,
)

insert into test1(name, course, score) values ('张三','语文', 80)
insert into test1(name, course, score) values ('张三','数学', 52)
insert into test1(name, course, score) values ('张三','英语', 150)
insert into test1(name, course, score) values ('李四','语文', 44)
insert into test1(name, course, score) values ('李四','数学', 111)
insert into test1(name, course, score) values ('李四','英语', 110)
insert into test1(name, course, score) values ('王五','语文', 140)
insert into test1(name, course, score) values ('王五','数学', 80)
insert into test1(name, course, score) values ('王五','英语', 92)
insert into test1(name, course, score) values ('王五','物理', 77)
insert into test1(name, course, score) values ('王五','化学', 65)

-- 使用case when then else ，这里也可以使用sum函数
select name,
max(case course when '语文' then score else 0 end) as chinese,
max(case course when '数学' then score else 0 end) as math,
max(case course when '英语' then score else 0 end) as english,
max(case course when '物理' then score else 0 end) as wuli,
max(case course when '化学' then score else 0 end) as huaxue
from test1 group by name

-- 使用pivot函数行转列
select name,max(t.语文)as chinese,max(t.数学)as math,max(t.英语)as english,max(t.物理)as wuli,max(t.化学)as huaxue
from test1  pivot(max(score) for course in(语文,数学,英语,物理,化学))t 
group by name

-- 第一种写法，动态sql拼接，有多少行可以进行动态拼接sql，在列不确定的情况下可以使用
declare @sql_str varchar(8000); -- 要执行的sql
declare @sql_col varchar(8000);
select @sql_col = isnull(@sql_col + ',','') + quotename(course) 
from test1 group by course;
print(@sql_col); -- 打印数值列,不必需
set @sql_str = 'select * from (select name,course,score from test1)p pivot(sum(score) for course IN ( '+ @sql_col +'))as pvt order by pvt.name'
print (@sql_str);--打印执行的sql
exec (@sql_str);-- 执行查询

--第二种写法
declare @name varchar(100);
declare @max varchar(1000);
declare @sql nvarchar(4000);
select @name= stuff(
(select ','+course+'' from test1  group by course  for xml path('')),1,1,'');
select @max= stuff(
(select ',max('+course+') as '+course+'' from test1 group by course for xml path('')),1,1,'');
set @sql='select name,'+@max+' from test1 pivot (max(score) for course in('+@name+')) css   group by name';
exec(@sql);

-- 使用distinct
select distinct  a.name,  
(select score from test1 b where a.name=b.name and b.course='语文' ) as 'chinese',  
(select score from test1 b where a.name=b.name and b.course='数学' ) as 'math',
(select score from test1 b where a.name=b.name and b.course='英语' ) as 'english',  
(select score from test1 b where a.name=b.name and b.course='物理' ) as 'wuli',  
(select score from test1 b where a.name=b.name and b.course='化学' ) as 'huaxue'  
from test1 a 

create table test2(
	id int identity(1,1) not null,
	name varchar(255) null,
	chinese int null,
	math int null,
	english int null,
	wuli int null,
	huaxue int null
) 

insert into test2(name,chinese,math,english,wuli,huaxue) values ('张三',110,120,85,null,null);
insert into test2(name,chinese,math,english,wuli,huaxue) values ('李四',130,88,89,null,null);
insert into test2(name,chinese,math,english,wuli,huaxue) values ('王五',93,124,87,98,67);

--第一种写法:	
select row_number() over(order by id desc) as id,name,t.course,t.score from(
	select id,name,course='语文',score=chinese from test2 union all
	select id,name,course='数学',score=math from test2 union all
	select id,name,course='英语',score=english from test2 union all
	select id,name,course='物理',score=wuli from test2 union all
	select id,name,course='化学',score=huaxue from test2
) t where score is not null order by id asc
-- 下面可以不用执行，执行上面即可
,case t.course when '语文' then 1 when '数学' then 2 when '英语' then 3 when '物理' then 4 when '化学' then 5 end

-- 第二种写法：
select row_number() over(order by id desc) as id,name,t.course,t.score from(
	select id,name,'语文' as course, chinese as 'score' from test2 union 
	select id,name,'数学' as course, math as 'score' from test2 union 
	select id,name,'英语' as course, english as 'score' from test2 union 
	select id,name,'物理' as course, wuli as 'score' from test2 union 
	select id,name,'化学' as course, huaxue as 'score' from test2
) t where score is not null order by id asc
-- 下面可以不用执行，执行上面即可
,case t.course when '语文' then 1 when '数学' then 2 when '英语' then 3 when '物理' then 4 when '化学' then 5 end

--使用unpivot进行列转行
select row_number() over(order by id desc) as id,name,score,course from test2 unpivot( score for course  in(chinese,math,english,wuli,huaxue))a