Question

Example database :

ID StudentName StudentClass
1  John        A
2  John        B
3  Peter       A
4  John        A
5  John        B

I want the result should be

ID StudentName StudentClass
1  John        A
2  John        B
3  Peter       A

Statment

DELETE FROM Student
 WHERE ID NOT IN (SELECT * 
                    FROM (SELECT MIN(n.ID)
                            FROM Student n
                        GROUP BY n.StudentName) x)

How do I keep John name on class A & B?

Answer 1

DELETE a FROM Student a
LEFT JOIN
    (
        SELECT MIN(ID) AS minid
        FROM Student
        GROUP BY StudentName, StudentClass
    ) b ON a.id = b.minid
WHERE
    b.minid IS NULL