一个表中重复数据的处理

查询、删除重复数据的SQL语句 MySQL 查询 columnName 有重复的数据，保留 id 最大的一个。SELECT MAX(id) AS id, columnName, COUNT(columnName ) AS countNumberFROM tableNameGROUP BY columnNameHAVING countNumber 1ORDER BY countNumber DESC;删除 colum

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查询   columnName 有重复的数据，保留  id  最大的一个。SELECT MAX(id) AS id, columnName, COUNT(columnName  ) AS countNumberFROM tableNameGROUP BY columnNameHAVING countNumber> 1ORDER BY countNumber DESC;删除  columnName  有重复的数据，保留  id  最小的一个。DELETE tableName t1FROM tableName t1, (SELECT min(id) id , columnName FROM tableName GROUP BY columnName HAVING COUNT(1) > 1 ) t2WHERE t1.columnName = t2.columnNameAND t1.   id > t2.id;

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