SELECT
    CASE
        WHEN a + b <= c OR a + c <= b OR b + c <= a THEN 'Not A Triangle'
        WHEN a <> b AND b <> c AND c <> a THEN 'Scalene'
        WHEN a = b AND b = c THEN 'Equilateral'
        WHEN (a = b AND a <> c) OR (a = c AND a <> b) OR (b = c AND c <> a) THEN 'Isosceles'
    END 
FROM triangles;