項目背景
最近做項目,發現oracle中存在重複數據,導致項目查詢結果冗餘,特此需要對數據進行去重。比如下面截圖所示:
場景一:根據單個字段(Id)來判斷重複記錄
1、查找表中多餘的重複記錄,重複記錄是根據單個字段(Id)來判斷
select * from 表 where Id in (select Id from 表 group by Id having count(Id) > 1);
2、刪除表中多餘的重複記錄,重複記錄是根據單個字段(Id)來判斷,只留有rowid最小的記錄
DELETE from 表 WHERE (id) IN (
SELECT id FROM 表 GROUP BY id HAVING COUNT(id) > 1)
AND ROWID NOT IN (
SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);
場景二:根據多個字段來判斷重複記錄
1、查找表中多餘的重複記錄(多個字段)
select * from 表 a where (a.Id,a.seq)
in(select Id,seq from 表 group by Id,seq having count(*) > 1);
2、刪除表中多餘的重複記錄(多個字段),只留有rowid最小的記錄
delete from 表 a where (a.Id,a.seq)
in (select Id,seq from 表 group by Id,seq having count(*) > 1)
and rowid not in (select min(rowid)
from 表 group by Id,seq having count(*)>1);
執行結果
場景三:多表關聯查詢,過濾重複數據記錄,相同記錄只查詢一條
原始記錄如下圖所示:
核心SQL語句如下:
SELECT
*
FROM
( SELECT row_number () over ( partition BY 分組的字段名 ORDER BY 排序字段名 DESC ) rn, 字段名 FROM 表名 )
WHERE
rn = 1
則經過過濾去重,查詢出結果爲: