Usefull Mysql

// Find Duplicate Rows//
SELECT 
    email, COUNT(email)
FROM
    contacts
GROUP BY 
    email
HAVING 
    COUNT(email) > 1;
// End //    

//Delete Duplicate Rows//
DELETE c1 FROM contacts c1
INNER JOIN contacts c2 
WHERE
    c1.id > c2.id AND 
    c1.email = c2.email;
// End //