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
 n2.ID AND n1.connection = n2.connection;

UPDATE `wp_posts' 
SET `post_type` = 'SMS'
WHERE `post_title` LIKE 'SMS%';