sql - 带有 in group by 或 partition by 子句的 case 语句

Question

Customer   Decision      req_date   
   A       Approved     2017-06-13
   A       Approved     2017-06-13
   A       Pending      2017-06-13
   B       Pending      2017-10-13
   B       Approved     2017-06-13
   C       Pending      2017-07-14

对于给定的客户 ID，

如果决定是已批准的，则只保留客户的批准行。如果客户没有任何已批准的决定，则保留客户的所有行。

期待输出

Customer   Decision      req_date   
   A       Approved     2017-06-13
   A       Approved     2017-05-13
   B       Approved     2017-06-13
   C       Pending      2017-07-14

Answer 1

我会使用或:

select t.*
from t
where t.decision = 'Approved' or
      not exists (select 1
                  from t t2
                  where t2.Customer = t.Customer and t2.decision = 'Approved'
                 );