Question

我想从下表中删除多个重复的密钥：

id | name   | uid
1  | ekta   | 5
2  | ekta   | 5
3  | sharma | 10
4  | sharma | 10

希望它像

id | name   | uid
1  | ekta   | 5
3  | sharma | 10

我正在使用mysql。可能吗？我无法使用unique constraint查询来创建唯一的输入，因为我希望将这些重复的条目输入到表中。

Answer 1

这样做的一种方法是使用LEFT JOIN在子查询上加入表。每个ID子查询得到最低UID。如果记录在子查询中没有匹配，则只表示它没有匹配的记录，可以安全删除。

DELETE  a
FROM    TableName a
        LEFT JOIN
        (
            SELECT  uid, MIN(ID) min_ID
            FROM    TableName
            GROUP   BY uid
        ) b ON  a.uid = b.uid AND
                a.ID = b.min_ID
WHERE   b.uid IS NULL

SQLFiddle Demo

但是，如果UID的记录可以有不同的名称，那么您需要在name子句中包含group by，或者只包含uid唯一ID { {1}}将保留。

DELETE  a
FROM    TableName a
        LEFT JOIN
        (
            SELECT  uid, MIN(ID) min_ID, name
            FROM    TableName
            GROUP   BY uid, name
        ) b ON  a.uid = b.uid AND
                a.ID = b.min_ID AND
                a.name = b.name
WHERE   b.uid IS NULL

Answer 2

  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;

删除表中的重复条目

2 个答案: