Question

我有一个包含userID, sectionId, usersectionID, valid列的表格。此有效列用于标识重复条目。但是有些重复的条目混合在有效列中。

select userID, sectionId, count(*) as cnt from table where valid = 1 group by 1,2 having cnt >1 ;

这将显示userID和sectionID组合重复条目的列表。如果userid和sectionID组合包含多个条目，则表示存在重复条目。

例如，这可能是输出，

userId      SectionID        Cnt
1               4             3

现在，当我们进一步看到这一点时，

Select userId, sectionId, usersectionID, valid from table where userID = 1 and sectionID = 4;

userID      sectionID   usersectionID   valid
1              4            3             1
1              4            5             1
1              4            10            1

我想用除了最小usersectionID之外的所有条目更新有效列为0。此查询后的输出应为

userID      sectionID   usersectionID   valid
1              4            3             1
1              4            5             0
1              4            10            0

我想在单个查询中为完整表执行此操作。我已经尝试了很长时间并取得了很大的成功。任何人都可以帮我解决这个问题吗？或者甚至可以在完成这项工作时给出一些想法？

由于

Answer 1

使用带有自JOIN的UPDATE来查找应标记为无效的重复项。

UPDATE table AS t1
JOIN (SELECT userID, sectionID, MIN(usersectionID) AS minusersectionID
      FROM table
      WHERE valid = 1
      GROUP BY userID, sectionID) AS t2 
ON t1.userID = t2.userID AND t1.sectionID = t2.sectionID AND t1.usersectionID != t2.minusersectionID
SET t1.valid = 0
WHERE t1.VALID = 1

Answer 2

您可以使用以下任何一种方法。

根据最低

更新

Update TableName
JOIN (
    SELECT userID, sectionID, MIN(userSectionID) AS minuserSectionID
    FROM TableName
    GROUP BY userID, sectionID
) AS T
Set Valid = 1
WHERE 
TableName.userID = T.userID
AND TableName.sectionID = T.sectionID
AND TableName.userSectionID = T.minuserSectionID;

或使用 根据排名第一的值进行更新

SET @rank=0;
Update TableName
JOIN (
    SELECT userID, sectionID, @rank:=@rank+1 AS rownumber
    FROM TableName
    GROUP BY userID, sectionID
) AS T
Set Valid = 1
WHERE 
TableName.userID = T.userID
AND TableName.sectionID = T.sectionID
AND T.rownumber = 1;

查找重复的条目并更新列 - Mysql

2 个答案: