从 2 列表（行到列）创建具有多列的表

Question

我有以下问题需要您的帮助才能使用资源表中的数据创建结果表

我有一个“资源”表：

Code	Value
A	100
B	100
C	220
A	150
C	300
D	120
E	120

使用 SQL 创建 'Result' 表：

Code1	Value1	Code2	Value2	Code3	Value3
A	100	B	100	C	220
A	150	C	300	D	120
E	120

我的想法是创建 3 个表然后加入它们，但我不知道如何获得第一、第二和第三行。有没有人有更优化的方法？

感谢您阅读我的问题！

Answer 1

您没有为行指定任何排序，因此我按(code, value) 对它们进行了排序。请记住，表中的行没有任何固有的顺序（例如，在电子表格中）。

你可以这样做：

with
x as (
  select *,
    (row_number() over(order by code, value) - 1) / 3 as line,
    (row_number() over(order by code, value) - 1) % 3 as col
  from t
)
select
  a.code as code1, a.value as value1,
  b.code as code2, b.value as value2,
  c.code as code3, c.value as value3
from x a
left join x b on b.line = a.line and b.col = 1
left join x c on c.line = a.line and c.col = 2
where a.col = 0;

结果：

 code1  value1  code2  value2  code3  value3 
 ------ ------- ------ ------- ------ ------ 
 A      100     A      150     B      100    
 C      220     C      300     D      120    
 E      120     null   null    null   null   

请参阅DB Fiddle 的运行示例。

Answer 2

架构和插入语句：

 create table Resource (Code varchar(10),   Value int);

 insert into Resource values('A',   100);
 insert into Resource values('B',   100);
 insert into Resource values('C',   220);
 insert into Resource values('A',   150);
 insert into Resource values('C',   300);
 insert into Resource values('D',   120);
 insert into Resource values('E',   120);

查询#1：

 with cte as 
 (
 select *,row_number()over(order by null) rn from Resource
 )
 select (case when rn%3=1 then code end) as Code1, (case when rn%3=1 then value end) as Value1
 ,(case when rn%3=2 then code end) as Code2, (case when rn%3=2 then value end) as Value2,
 (case when rn%3=0 then code end) as Code3, (case when rn%3=0 then value end) as Value3
  from cte 

输出：

Code1	Value1	Code2	Value2	Code3	Value3
A	100	null	null	null	null
null	null	B	100	null	null
null	null	null	null	C	220
A	150	null	null	null	null
null	null	C	300	null	null
null	null	null	null	D	120
E	120	null	null	null	null

查询#2

 with cte as 
 (
 select *,row_number()over(order by null) rn from Resource
 )
 ,Code1 as 
  ( 
  select Code Code1, value  Value1
  , row_number()over(order by null) rownumber
  from cte n where rn%3=1
  )
 ,Code2 as
  ( 
  select Code Code2, value  Value2
  , row_number()over(order by null) rownumber
  from cte n where rn%3=2 
  )
 ,Code3 as
  ( 
  select Code Code3, value  Value3
  , row_number()over(order by null) rownumber
  
  from cte n where rn%3=0
  )
  
  select *,code1.rownumber from Code1 left join Code2 on Code1.rownumber=Code2.rownumber
  left join Code3 on Code2.rownumber = Code3.rownumber
  
  
  

Code1	Value1	rownumber	Code2	Value2	rownumber	Code3	Value3	rownumber	rownumber
A	100	1	B	100	1	C	220	1	1
A	150	2	C	300	2	D	120	2	2
E	120	3	null	null	null	null	null	null	3

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