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©Copyright 蕃薯耀 2023-01-31

蕃薯耀的博客_CSDN博客-蕃薯耀分享,java,js领域博主

一、Mysql 删除重复数据保留一条有效数据

DELETE FROM SZ_Building WHERE id NOT IN (
  SELECT t.min_id FROM (
    SELECT MIN(id) AS min_id FROM SZ_Building GROUP BY BLDG_NO
  ) t
)
;

原理

1. 根据字段对数据进行分组查询出所有分组的最小ID即要保留的不重复数据
2. 将查询出来的数据所有不重复的数据存放到临时表中
3. 从原来的表中删除ID不在临时表中的重复数据

二、Mysql 删除重复数据多个字段分组

DELETE FROM SZ_Water_Level WHERE id NOT IN (
  SELECT t.min_id FROM (
    SELECT MIN(id) AS min_id FROM SZ_Water_Level GROUP BY CZBM,SJ,SW
  ) t
)
;

三、Mysql 查询出可以删除的重复数据

SELECT * FROM SZ_Building WHERE BLDG_NO IN (
	SELECT BLDG_NO FROM SZ_Building GROUP BY BLDG_NO HAVING COUNT(1)>1
) 
AND id NOT IN (
	SELECT MIN(id) FROM SZ_Building GROUP BY BLDG_NO HAVING COUNT(1)>1
)
;

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©Copyright 蕃薯耀 2023-01-31

蕃薯耀的博客_CSDN博客-蕃薯耀分享,java,js领域博主