CREATE TABLE contacts (
id INT,
email varchar(100)
);
INSERT INTO contacts (id,email) VALUES (1,'aaa@aaa.com');
INSERT INTO contacts (id,email) VALUES (2,'bbb@aaa.com');
INSERT INTO contacts (id,email) VALUES (3,'cc@aaa.com');
INSERT INTO contacts (id,email) VALUES (4,'bbb@aaa.com');
INSERT INTO contacts (id,email) VALUES (5,'aaa@aaa.com');
INSERT INTO contacts (id,email) VALUES (6,'ddd@aaa.com');
INSERT INTO contacts (id,email) VALUES (7,'aaa@aaa.com');
INSERT INTO contacts (id,email) VALUES (8,'ccc@aaa.com');
INSERT INTO contacts (id,email) VALUES (9,'aaa@aaa.com');
INSERT INTO contacts (id,email) VALUES (10,'bbb@aaa.com');
DELETE e1 FROM contacts e1, contacts e2 WHERE e1.id > e2.id AND e1.email = e2.email;
SELECT * FROM contacts;