Question

I have the following SQL statement which seems to be deleting every row in the selected table. What it should be doing is deleting all but the top 10 where the difficulty level equals one.

DELETE FROM Scores
WHERE Highscore_ID 
NOT IN (SELECT TOP 10 highScore FROM Scores WHERE difficulty = 1 ORDER BY HighScore DESC)

Any suggestions as to why this would be deleting all rows? When running the subquery, it selects the proper rows, however, when deleting, it seems to want to delete every row.

Answer 1

You compare Hichscore_Id with a column highScore. Does those columns really have the same values?

Then it should be

DELETE FROM Scores 
WHERE Highscore_ID NOT IN
          (SELECT TOP 10 HighScore_ID 
           FROM Scores 
           WHERE difficulty = 1 
           ORDER BY HighScore DESC);

EDIT:

Try this

DELETE FROM Scores
JOIN (SELECT ROW_NUMBER() OVER (ORDER BY highscore) AS your_row, * 
      FROM Scores 
      WHERE difficulty = 1 
      ORDER BY HighScore DESC) AS score2 ON score2.HighScore_ID = Scores.HighScore_ID
WHERE Scores.difficulty = 1 AND score2.your_row>10