Correction; Considered a warning.
Here is a good rule-of-thumb: If you have to write an SQL with Select Distinct, do adjust your chair, get a cup of coffee, walk around the office but above all talk to someone else because Select Distinct is a symptom of something being wrong, either in the database or in your solution.
/* Select Distinct is normally not needed when your database is lagom normalized. But if you do need a Select Distinct then this is a very good example of a situation that needs to be documented.*/