Delete Duplicate
DELETE n1 FROM connections n1, connections n2 WHERE n1.ID > n2.ID AND n1.connection = n2.connection;
Update Specific Column
UPDATE `column-name' SET `column-name`= NULL
DELETE n1 FROM connections n1, connections n2 WHERE n1.ID > n2.ID AND n1.connection = n2.connection;
UPDATE `column-name' SET `column-name`= NULL