Filtering out duplicate values

I'm filtering a large table.. one of the fields is filtered by the expression: <>"" AND <>"NA" it works fine, but now I need to filter that same field so that it doesnt include any values that repeat.. what do i need to add to the expression to do this?

Thanks,
Alan

I'm not sure I understand what you want. You want all rows exclude where values in that specific column occur more then once?

This should work (not tested)

SELECT *
FROM table
WHERE col1 <> ""
AND col1 <> "NA"
AND col1 NOT IN
(SELECT col1
FROM table1
GROUP BY col1
HAVING count(*) > 1);

But this will remove any row where the content of col1 exists more then once (it will not even return one of those rows)

use "Not Exist" instead of "Not In" to avoid full table scan.
(if shammat's code is working)