DB2从具有列名的非空列中选择

Question

DB2中有一个包含以下数据的表：

Location|Phone|Email  |Changedatetime
null    |3314 |null   |12/07/2019 10:00
null    |null |e@e.com|12/07/2019 11:00

这是相关表中的更改列表。 我需要基于此表的选择，列名称和值不能为空

如果可能，我需要通过以下方式选择它：

Attribute|Value  |Changedatetime
Phone    |3314   |12/07/2019 10:00
Email    |e@e.com|12/07/2019 11:00

Answer 1

一种方法可能是使用union

select 'Phone' as attribute, Phone as value, Changedatetime
from tablename where phone is not null
union 
select 'Email', email, Changedatetime
from tablename where email is not null

Answer 2

用例声明。

select 
case when Phone is not null then 'Phone' else 'Email' end as Attribute , 
case when Phone is not null then Phone  else Email end as Value ,
Changedatetime
from tablename