SQL左外部加入一对多行

Question

我有两个表。帐户表和交易表。我想列出所有账户与他们的最后交易。由于没有事务的情况下可能存在需要左连接。

我有类似

select * from Account ac left join Transaction trans on ac.id = trans.acc_id 

但是，这将列出所有的交易数据。不知道如何修改它。

Answer 1

第一左连接让你帐户的最后\最大事务ID。第二个左连接为您获取最后一个ID的所有交易信息。

select ac.*, lasttrans.* 
from Account ac 
left join (select acc_id, max(id) as id from Transaction group by acc_id) transmax 
    on ac.id = transmax.acc_id 
left join Transaction lasttrans on lasttrans.id = transmax.id 

Answer 2

沿着只需使用一个aggregate功能与group by

select * from 
from Account ac left join Transaction trans 
on ac.id = trans.acc_id 
where trans.id in (select max(id) from trans group by ac.id) 

编号或日期这有史以来的是，你想获得的max的列..

Answer 3

您可以通过连接Account表试试只有交易表的acc_id对应于每个acc_id的最大ID：

 select ac.*, t.* from Account ac left join (select acc_id, max(id) from Transaction group by acc_id) trans on ac.id = trans.acc_id left join Transaction t on trans.id=t.id 

Answer 4

这是否接近你在期待什么？

with acc as 
(select 1 acc_id, 'name1' acc_name from dual union 
select 2 acc_id, 'name2' acc_name from dual union 
select 3 acc_id, 'name3' acc_name from dual), 
trans as 
(select 1 trans_id, 1 trans_acc_id, 'transaction detail 1' transdtl from dual 
union 
select 2 trans_id, 1 trans_acc_id, 'transaction detail 2' transdtl from dual 
union 
select 3 trans_id, 1 trans_acc_id, 'transaction detail 3' transdtl from dual 
union 
select 4 trans_id, 3 trans_acc_id, 'transaction detail 4' transdtl from dual 
union 
select 5 trans_id, 5 trans_acc_id, 'transaction detail 5' transdtl from dual 
) 
select * from acc, trans 
where acc.acc_id = trans.trans_acc_id 
and trans.trans_id in (select max(trans_id) from trans inner_trans where 
inner_trans.trans_acc_id = acc.acc_id) 

他们的回应是：

ACC_ID|ACC_NAME|TRANS_ID|TRANS_ACC_ID|TRANSDTL 
1 |name1 |3 |1 |transaction detail 3 
3 |name3 |4 |3 |transaction detail 4