Rule Definition
Identify "DISTINCT", "DISTINCTROW", "UNIQUE" modifiers in SQL "SELECT" statements: - is frequently a "code smell" - it indicates that something is not quite right because using the DISTINCT keyword means that redundant data is being pulled from the database and then discarded - applicable for all sql, including embedded sql

Remediation
Check the statement and if so, rearrange the "WHERE" or the "FROM" clause in the SQL "SELECT" statement to only get the rows you need.

Violation Code Sample

The following SQL "SELECT" statement should be reviewed:
SELECT DISTINCT u.user_id, u.user_name, u.realname, u.email, u.confirm_hash 
FROM users u, user_group ug, groups g 
WHERE u.status='A' 
 AND u.user_id=ug.user_id 
 AND ug.admin_flags='A' 
 AND g.status='A' 
 AND g.group_id=ug.group_id 
ORDER BY u.user_id;

Fixed Code Sample

Add an uncorrelated subquery:
SELECT u.user_id, u.user_name, u.realname, u.email, u.confirm_hash
FROM users u 
WHERE u.status = 'A' 
 AND u.user_id 
 IN (
  SELECT ug.user_id 
  FROM user_group ug, groups g 
  WHERE ug.admin_flags='A' 
   AND g.status = 'A' 
   AND g.group_id = ug.group_id
  )
ORDER BY u.user_id;