#sql
SELECT DISTINCT * FROM Mytable;

#sql
--если колонкам m и e присвоено значение NOT NULL
INSERT INTO Mytable (m,e) VALUES ((SELECT 1 WHERE NOT EXISTS  (SELECT m,e FROM Mytable WHERE m = 1 AND e=2)), (SELECT 2 WHERE NOT EXISTS  (SELECT m,e FROM Mytable WHERE m = 1 AND e=2)));