MySql根据字段名查询重复记录并删除！只保留一条

Posted 2022-08-04 java李杨勇

最近在处理业务数据的时候！在几W条记录里存在着些相同的记录,如何用SQL语句,删除掉重复的呢?

可以用以下方法进行处理

其实很简单！就是查找表中多余的重复记录，重复记录是根据单个字段来查询、然后删除其他重复的记录即可

查询重复记录

SELECT  id ,title from  topic GROUP BY title HAVING count(*) > 1;

这样查出来的结果比较乱

查询全部的重复记录并分组

​​​​SELECT
	* 
FROM
	topic 
WHERE
	title IN ( SELECT title FROM topic GROUP BY  title HAVING Count(*)> 1 ) 
	AND title IN (
	SELECT
		title 
	FROM
		topic 
	GROUP BY
		title
HAVING
	count(*)> 1) ORDER BY title

对查询结果进行分组根据需要的字段 

查询除第一条外的多余数据

SELECT
	*
FROM
	topic
WHERE
	id NOT IN (
		SELECT
			dt.minId
		FROM
			(
				SELECT
					MIN(id) AS minId
				FROM
					topic
				GROUP BY
				title
			) dt
	)
ORDER BY
	title

删除第一条外的多余数据

DELETE
FROM
	topic
WHERE
	id NOT IN (
		SELECT
			dt.minId
		FROM
			(
				SELECT
					MIN(id) AS minId
				FROM
					topic
				GROUP BY
					title
			) dt
	)
ORDER BY
	title