如何在3个表的联接中映射一个人（每个表是一年）

Question

因此，如果之前有人问过我，我事先表示歉意...

1. 我有3个表，每个表都有People X Attributes（LxW）的维度。这些属性包括acc_balance，withdrawals，contributions，birth_year等
之类的内容。
2. 每张桌子都是一年（2016，17，18）。
3. 目标是在最终表中，每年通过Person_ID将个人与每年的Person_ID，Account_ID和Transactions列相关联，类似于以下内容：

由于此人始终具有相同的ID，所以只有“人”会更干净。

注意事项：

1. 一个人可能有多个帐户（想通过Person_ID分组）
2. 想拥有Person =（Personal_id2018 = Personal_id2017 = Personalid2016）]

我尝试过的：

select person = personal_id, 
       Accounts18 = count(a.Account_ID), 
       Accounts17 = count(b.Account_ID), 
       Accounts16 = count(c.Account_ID), 
       Transac18 = a.Transactions, 
       Transac17 = b.Transactions, 
       Transac16 = c.Transactions
from
    (select personal_id, account_id, transactions from dbo.bank2018 group by personal_id) a
inner join
    (select personal_id, account_id, transactions from dbo.bank2017 group by personal_id) b
on a.personal_id = b.personal_id
inner join
    (select personal_id, account_id, transactions from dbo.bank2016 group by personal_id) c
on b.personal_id = c.personal_id
group by person???

谢谢大家！

Answer 1

我认为您希望每一列都计数。如果是这样，则所有工作都在子查询中完成：

select b2018.personal_id, b2018.num_accounts_2018, b2018.num_transactions_2018,
       b2017.num_accounts_2017, b2017.num_transactions_2017,
       b2016.num_accounts_2016, b2016.num_transactions_2016
from (select personal_id,
             count(distinct account_id) as num_accounts_2018,
             count(*) as num_transactions_2018
       from dbo.bank2018
       group by personal_id
      ) b2018 inner join
      (select personal_id,
             count(distinct account_id) as num_accounts_2017,
             count(*) as num_transactions_2017
       from dbo.bank2017
       group by personal_id
      ) b2017
      on b2017.personal_id = b2018.personal_id inner join
      (select personal_id,
             count(distinct account_id) as num_accounts_2016,
             count(*) as num_transactions_2016
       from dbo.bank2016
       group by personal_id
      ) b2016
      on b2016.personal_id = b2017.personal_id;

注意，这只会返回在所有三个表中都有数据的人。如果希望一个或多个表中缺少的客户，则需要某种外部联接。