I need some help here.

Currently I have this sql statement

$sql_reviewing = "SELECT * FROM EVALUATION_TABLE where status in ('Reviewing') and expiry_date < '$today' order by ref_no asc";

ref_no is the number of a paper and this paper can be reviewed by a few reviewers. For any particular paper, some reviewers might have reviewed (status) the paper while some have not. Right now, I want to extract the paper info with the ref_no where at least one reviewers has not reviewed the paper (as such status remains at reviewing).

The above sql will return multiple times of the same ref_no. However, what I need is for the ref_no to be returned once.

Return ref_no once even if there are multiple records with the same ref_no

Which means that if there are 2 or more reviewers who are still reviewing the same particular paper (same ref_no), this ref_no will be selected once only.

Hope that is clear.

Thanks and any advise is most appreciated.