在 ORACLE 中将 sql 查询从宽格式转换为长格式

Question

我有一个这样的 sql 查询

select
 group, 
sum(case when field1 = 'a' then 1 else 0 end ) as typea,
sum(case when field1 = 'b' then 1 else 0 end ) as typeb
from mytable
group by group

结果是这样的

group  typea    typeb
 1      10         30
 2      20          40

效果很好，但我需要这样的结果：

group  types     value
1       typea     10
2       typea      30
1       typeb      20
2       typeb      40

有没有办法修改这个查询：

select
 group, 
sum(case when field1 = 'a' then 1 else 0 end ) as typea,
sum(case when field1 = 'b' then 1 else 0 end ) as typeb
from mytable
group by group

以便它返回我需要的结果？

注意——我正在使用 ORACLE

谢谢。

Answer 1

使用UNION ALL：

select "group", 
      'typea' AS type,
       sum(1) AS value
from mytable
where field1 = 'a'
group by "group"
UNION ALL
select "group", 
       'typeb',
       sum(1)
from mytable
where field1 = 'b'
group by "group"

Answer 2

数据已经正确组织，您只需进行不同的分组。

SELECT "group", 'type'||field1 as Types, sum(1) as value
FROM mytable
GROUP BY "group", 'type'||field1
ORDER BY Types, "group"

注意组是保留字，所以我把它放在“”中，如果它的列和类型可以重命名，你最好长期使用，因为一个是保留字，另一个是关键字。

With MyTable("group",field1) as  (select 1, 'a' from dual UNION ALL
select 1 , 'a' as field1 from dual UNION ALL
select 1 , 'b' as field1 from dual UNION ALL
select 1 , 'b' as field1 from dual UNION ALL
select 2 , 'a' as field1 from dual UNION ALL
select 2 , 'a' as field1 from dual UNION ALL
select 2 , 'a' as field1 from dual UNION ALL
select 2 , 'b' as field1 from dual)
SELECT "group", 'type'||field1 as Types, sum(1) as value
FROM mytable
GROUP BY "group", 'type'||field1

虽然你为什么需要连接'type'作为field1的前缀是奇怪的。它可能只是一个简单的（无旋转）计数，并且似乎只需要分组。

SELECT "group", field1 as Types, count(*) as value
FROM mytable
GROUP BY "group", field1
ORDER BY Types, "group"