SQL如何修改此表

Question

如何在sql中获取此表：

id   cunsumption_bhd cunsumption_metha 
id1  21.0            10.2

从此表：

id   type   cunsumption
id1  bhd    21.0
id1  metha  10.2

Answer 1

对表的两个“实例”都使用带有类型过滤器的自联接。

select t1.id, 
       t1.consumption as consumption_bhd, 
       t2.consumption as consumption_metha
from the_table t1
  join the_table t2 on t1.id = t2.id and t2.type = 'metha'
where t1.type = 'bhd'
  and t1.id = 'id1';

Answer 2

一种方法是条件聚合：

select max(case when type = 'bhd' then consumption end) as consumption_bhd,
       max(case when type = 'metha' then consumption end) as consumption_metha
from t;