Find duplicate mysql record and update first duplicate with last duplicate value

i have a table like this.

ID    Name     Tag    
1     Orange   tea     
2     Pear     light   开发者_如何学JAVA 
3     Apple    tea
4     Juice    tea
5     Cocoa    baseball
6     Camera   baseball

What I want to do is for rows that have duplicate TAGS, I want to update the name of FIRST occurence with the LATEST occurence.

So in example above, I would like to update ID 1's name from Orange to Juice and delete the others (#3,#4) And update ID 5 from Cocoa to Camera and delete #6.

How would I do that using MySQL with PHP? Or maybe possible to just do it inside MySQL?

Thanks!

---

For the UPDATE query, we need to get the min and max ID's for each tag, only if there are duplicate rows:

UPDATE table t
  JOIN (
    SELECT MinID, b.Name LatestName
    FROM table b
    JOIN (
      SELECT MIN(ID) MinID, MAX(ID) MaxID
      FROM table
      GROUP BY tag
      HAVING COUNT(*) > 1
    ) g ON b.ID = g.MaxID
  ) rs ON t.ID = rs.MinID
SET t.Name = LatestName;

For the DELETE query, we delete all rows that are not the first ID's of its tag group:

DELETE t.*
FROM table t
  LEFT JOIN (
    SELECT MIN(ID) MinID
    FROM table
    GROUP BY tag
  ) g ON t.ID = g.MinID
WHERE g.MinID IS NULL;