MySQL或Postgres中的透视表

我们如何从

到

与此相反的是：

示例数据：

create table test (
    custname text, 
    computer numeric, 
    monitor numeric, 
    software numeric);

insert into test values
('Alison', 345.89, 123.45, 78.78),
('Jason', 435.34, 158.23, 243.54);

查询：

select 
    custname "Customer", 
    unnest(array['Computer', 'Monitor', 'Software']) "Item type",
    unnest(array[computer, monitor, software]) "Amount"
from test;

 Customer | Item type | Amount 
----------+-----------+--------
 Alison   | Computer  | 345.89
 Alison   | Monitor   | 123.45
 Alison   | Software  |  78.78
 Jason    | Computer  | 435.34
 Jason    | Monitor   | 158.23
 Jason    | Software  | 243.54
(6 rows)

---

如果

unnest（）

不可用，您可以使用

union

：

select custname "Customer", 'Computer' "Item type", computer "Amount" from test
union select custname, 'Monitor', monitor from test
union select custname, 'Sofware', software from test
order by 1, 2;

---

谢谢你的回答，如果我在MySql或Redshift（没有最不必要的功能）中这样做，我会怎么做？太棒了！感谢Klin:）生成MySQL代码：；