如何从oracle中的联接查询中删除重复的行？

Question

我有两个表bc_transactions和bc_messages。我使用下面的查询来连接这两个表

SELECT distinct(bt.USER_TRANS_ID),bm.TS,bm.STATUS
FROM bc_transactions bt
inner JOIN bc_messages bm
ON bt.USER_TRANS_ID=bm.USER_MESSAGE_ID
where bt.protocol_name  = 'Gateway'
and bt.STATUS=bm.STATUS
AND bt.startdate >=TRUNC(SYSDATE-2)
AND bt.startdate <=TRUNC(SYSDATE-1)
AND bt.STATUS like 'ERROR TRANSPORT'
AND bt.HOSTNAME='HEB'
order by bt.USER_TRANS_ID ASC;

bc_messages表具有状态为ERROR TRANSPORT的多行，这些行在不同的时间戳记（bm.TS）具有相同的USER_MESSAGE_ID。我正在尝试仅获取最新行。

|USER_TRANS_ID |            TS        |   STATUS            |
-------------------------------------------------------------
| ID1          | 10-03-2020  15:01:23 |   ERROR TRANSPORT   |
| ID1          | 10-03-2020  15:15:23 |   ERROR TRANSPORT   |
| ID1          | 10-03-2020  15:30:23 |   ERROR TRANSPORT   |
| ID1          | 10-03-2020  15:35:23 |   ERROR TRANSPORT   |
| ID2          | 10-03-2020  16:10:23 |   ERROR TRANSPORT   |
| ID2          | 10-03-2020  16:11:23 |   ERROR TRANSPORT   |

Answer 1

select t.*
from (select bt.USER_TRANS_ID, bm.TS,bm.STATUS,
             row_number() over (partition by bt.USER_TRANS_ID order by bm.TS desc) as seq
      from bc_transactions bt inner join
            bc_messages bm
            on bt.USER_TRANS_ID = bm.USER_MESSAGE_ID
       where bt.protocol_name  = 'Gateway' and 
             bt.STATUS=bm.STATUS and 
             bt.startdate >= TRUNC(SYSDATE-2) and 
             bt.startdate <= TRUNC(SYSDATE-1) and 
             bt.STATUS like 'ERROR TRANSPORT' and 
             bt.HOSTNAME = 'HEB'
     ) t
where seq = 1;

Answer 2

SELECT USER_TRANS_ID, TS, STATUS FROM 
(SELECT bt.USER_TRANS_ID,bm.TS,bm.STATUS, 
ROW_NUMBER() OVER (PARTITION BY bt.USER_TRANS_ID , bm.STATUS 
                   ORDER BY bm.TS DESC NULLS LAST) AS RN -- added this
FROM bc_transactions bt
inner JOIN bc_messages bm
ON bt.USER_TRANS_ID=bm.USER_MESSAGE_ID
where bt.protocol_name  = 'Gateway'
and bt.STATUS=bm.STATUS
AND bt.startdate >=TRUNC(SYSDATE-2)
AND bt.startdate <=TRUNC(SYSDATE-1)
AND bt.STATUS like 'ERROR TRANSPORT'
AND bt.HOSTNAME='HEB')
WHERE RN = 1 -- added this
order by bt.USER_TRANS_ID ASC;

干杯！