oracle怎么查询重复的数据

前言

Oracle 19c版本
在oracle中，可以利用count()函数配合select查询语句来查询重复的数据，语法为 :

select userCode from user group by userCode having count(userCode)>1

---

1、查找表中多余的重复记录，重复记录是根据单个字段（userCode）来判断

SELECT *
FROM user
WHERE userCode IN (
	SELECT userCode
	FROM user
	GROUP BY userCode
	HAVING count(userCode) > 1
);

2、删除表中多余的重复记录，重复记录是根据单个字段（userCode）来判断，只留有rowid最小的记录

DELETE FROM user
WHERE userCode IN (
		SELECT userCode
		FROM user
		GROUP BY userCode
		HAVING count(peopleId) > 1
	)
	AND rowid NOT IN (
		SELECT min(rowid)
		FROM user
		GROUP BY userCode
		HAVING count(userCode) > 1
	);

3、查找表中多余的重复记录（多个字段）

SELECT *
FROM user a
WHERE (a.userCode, a.userName) IN (
	SELECT userCode, userName
	FROM user
	GROUP BY userCode, userName
	HAVING count(*) > 1
);

4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录

DELETE FROM user a
WHERE (a.userCode, a.userName) IN (
		SELECT userCode, userName
		FROM user
		GROUP BY userCode, userName
		HAVING count(*) > 1
	)
	AND rowid NOT IN (
		SELECT min(rowid)
		FROM user
		GROUP BY userCode, userName
		HAVING count(*) > 1
	);

5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录

SELECT *
FROM user a
WHERE (a.userCode, a.userName) IN (
		SELECT userCode, userName
		FROM user
		GROUP BY userCode, userName
		HAVING count(*) > 1
	)
	AND rowid NOT IN (
		SELECT min(rowid)
		FROM user
		GROUP BY userCode, userName
		HAVING count(*) > 1
	);

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总结

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参考1