Select records based on column priority

Question

First of all, the title of this question is horrible, but I didn\'t find a better way to describe my issue.

There\'s probably a very easy way to do this, but I couldn\'t

Answer 1

Try this

SELECT * 
FROM xx
WHERE COLOUR = 'GREEN'
UNION
SELECT * 
FROM xx WHERE P_Id not in 
                (SELECT P_Id
                 FROM Persons 
                 WHERE COLOUR = 'GREEN');

See ALSO SQL FIDDLE DEMO