SQL Query Duplicate Removal Help

Question

I need to remove semi duplicate records from the following table

ID      PID      SCORE
1       1        50
2       33       20
3       1        90
4       5             


        

Answer 1

WITH    q AS
        (
        SELECT  *, ROW_NUMBER() OVER (PARTITION BY pid ORDER BY score) AS rn
        FROM    mytable
        )
DELETE
FROM    q
WHERE   rn = 1

To leave the results that have no duplicates:

WITH    q AS
        (
        SELECT  *,
                ROW_NUMBER() OVER (PARTITION BY pid ORDER BY score) AS rn,
                COUNT(*) OVER (PARTITION BY pid) AS cnt
        FROM    mytable
        )
DELETE
FROM    q
WHERE   rn = 1
        AND cnt > 1