根据某些列字段从表中删除重复行的 MySql 查询？

Question

我的表名是虚拟的，它包含 6 列，其中 ID、NAME、TIMESTAMP 和其他 3 列。

我想删除 ID、NAME 和 TIMESTAMP 值与其他行匹配的重复行。如果有多行具有相同的 ID、NAME 和 TIMESTAMP 值，则保留一并删除其他行。

Answer 1

解决办法

https://stackoverflow.com/a/5016434

我刚刚遇到的另一种可能的解决方案：

DELETE n1 FROM names n1, names n2 WHERE n1.id > n2.id AND n1.name = n2.name

如果要保留 id 值最低的行或

DELETE n1 FROM names n1, names n2 WHERE n1.id < n2.id AND n1.name = n2.name

https://stackoverflow.com/a/5770309

DELETE DupRows.*
FROM MyTable AS DupRows
   INNER JOIN (
      SELECT MIN(ID) AS minId, col1, col2
      FROM MyTable
      GROUP BY col1, col2
      HAVING COUNT(*) > 1
   ) AS SaveRows ON SaveRows.col1 = DupRows.col1 AND SaveRows.col2 = DupRows.col2
      AND SaveRows.minId <> DupRows.ID;

Answer 2

这是一个示例代码。这将帮助您完成它。

DELETE duplicate_rows.*
FROM dummy AS duplicate_rows
   INNER JOIN (
      SELECT MIN(id) AS id, name, timestamp
      FROM dummy
      GROUP BY session_id, user_id, category_id
      HAVING COUNT(*) > 1
   ) AS unique_rows 
ON unique_rows.session_id = duplicate_rows.session_id 
AND unique_rows.user_id = duplicate_rows.user_id
AND unique_rows.category_id = duplicate_rows.category_id
AND unique_rows.id <> duplicate_rows.id;

你可以在这里找到更详细的解释：http://mildcoder.com/delete-duplicate-rows-from-a-mysql-table/