Question

我有下面的表格和数据，

Create table transpose (a number, b number, c number); 

insert into transpose values (1,4,7);
insert into transpose values (2,5,8); 
insert into transpose values (3,6,9); 
commit; 
select * from transpose; 

A B C 
1 4 7 
2 5 8 
3 6 9

问题：我需要使用sql查询下面的输出，这是否可能反转数据（转置数据）？

请帮忙解决此问题。

Answer 1

有两件重要的事情需要考虑。

1）SQL表没有隐含的顺序，因此您必须添加 order by 信息以唯一地定义转置表的列。（我在表格中添加了一个列ID来模拟它。）

2）如果您正在寻找固定数量的列和行的解决方案，您可以在SQL查询中对结果进行编码，如下所示（对于动态解决方案，我不建议使用SQL）

 select 
   (select a from transpose where id = 1) a,
   (select a from transpose where id = 2) b,
   (select a from transpose where id = 3) c
 from dual
 union all
 select 
   (select b from transpose where id = 1) a,
   (select b from transpose where id = 2) b,
   (select b from transpose where id = 3) c
 from dual
 union all
 select 
   (select c from transpose where id = 1) a,
   (select c from transpose where id = 2) b,
   (select c from transpose where id = 3) c
 from dual;

     A          B          C
 ---------- ---------- ----------
     1          2          3 
     4          5          6 
     7          8          9

更新 - 使用PIVOT的解决方案

正如@WW在这里提出的带有数据透视的解决方案

 with trans as (
 /* add one select for each column */
 select id, 'A' col_name, a col_value from transpose union all
 select id, 'B' col, b col_value from transpose union all
 select id, 'C' col, b col_value from transpose)
 select * from trans
 PIVOT (sum(col_value) col_value 
 for (id) in 
 (1 as "C1", /* add one entry for each row (ID) */
 2 as "C2",
 3 as "C3" )
 )

使用Oracle SQL查询进行数据转置

1 个答案: