What is the difference in price between HL Mountain Frame - Black, 42 and LL Mountain Frame - Black, 42?
difference = SUBTRACT((Price WHERE Name = 'HL Mountain Frame - Black, 42'), (Price WHERE Name = 'HL Mountain Frame - Black, 42'));
SELECT ( SELECT Price FROM Products WHERE Name = 'HL Mountain Frame - Black, 42' ) - ( SELECT Price FROM Products WHERE Name = 'LL Mountain Frame - Black, 42' ) AS num