创建一个select来“去规格化”表中的数据

Question

我把工作去标准化为引号，因为它可能不是正确的放置方式，但不太确定如何描述它。 ..

我有以下表

Source Priority Attribute 
A  1   Name 
B  2   Name 
C  3   Name 
A  1   Address 
B  2   Address 
C  3   Address 
A  2   Email 
B  3   Email 
C  1   Email 

我想我的选择返回：

Source Name_Pri Addr_Pri Email_Pri 
A  1   1   2 
B  2   2   3 
C  3   3   1  

感谢

Answer 1

您正在寻找一个支点。我经常使用条件聚合来做到这一点：

select source, 
     max(case when attribute = 'Name' then priority end) as name_priority, 
     max(case when attribute = 'Address' then priority end) as address_priority, 
     max(case when attribute = 'Email' then priority end) as email_priority 
from t 
group by source;