Deleting all but top 10 rows - sql

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

Answer 2

Don't know if this is a typo or a real error but your select clause should refer to highscore_id, not highscore.

Answer 3

Try this:
with a as
(
select ROW_NUMBER() over(order by name) as ordinal, * from test
)
delete from a where a.ordinal > 10;
Related: http://www.ienablemuch.com/2012/03/possible-in-sql-server-deleting-any-row.html
Sample data:
CREATE TABLE [beatles]
([name] varchar(14));
INSERT INTO [beatles]
([name])
VALUES
('john'),
('paul'),
('george'),
('ringo'),
('pete'),
('brian'),
('george martin');
Query:
with a as
(
select *, row_number() over(order by name) ordinal
from beatles
)
delete from a
where ordinal > 4;
select * from beatles;
Prior deleting:
NAME
brian
george
george martin
john
paul
pete
ringo
After deleting:
NAME
brian
george
george martin
john
Live test: http://www.sqlfiddle.com/#!3/0adcf/6

Answer 4

My first guess would be "SELECT TOP 10 highScore FROM Scores WHERE difficulty = 1 ORDER BY HighScore DESC" could be returning null.
My second guess would be "highscore_id" is different from "highscore", so there's no overlap (and nothing's deleted).
Definitely double-check your subquery, and make sure it's returning the keys you expect!