Question

For some reason, I’d like to change the database.

It’s not possible to change these values manually one by one as there are so much records.

Please advise how to write this SQL, thanks.

From:

 id  percentage    type
  1     6        services
  1     10       testing
  3     8        services
  3     20       testing
  6     61       services
  6     90       testing

To:

id percentage    type
1     10       services
1     10       testing
3     20       services
3     20       testing
6     90       services
6     90       testing

Answer 1

If you want to select only see Mahmoud Gamal’s Answer

But if you want to permanently change the value, Use UPDATE

UPDATE  tableName a
        INNER JOIN
        (
            SELECT id, MAX(percentage) AS maxPercentage
            FROM tableName
            GROUP BY id
        ) b ON a.ID = b.ID
SET a.percentage = b.maxPercentage;

• SQLFiddle Demo