[HackerRank|MySQL] Type of Triangle

Type of Triangle

Problem

Write a query identifying the type of each record in the TRIANGLES table using its three side lengths. Output one of the following statements for each record in the table:

• Equilateral: It's a triangle with sides of equal length.
• Isosceles: It's a triangle with sides of equal length.
• Scalene: It's a triangle with sides of differing lengths.
• Not A Triangle: The given values of A, B, and C don't form a triangle.

Input Format

The TRIANGLES table is described as follows:

Each row in the table denotes the lengths of each of a triangle's three sides.

Sample Input

Sample Output

Isosceles
Equilateral
Scalene
Not A Triangle

Explanation

Values in the tuple (20, 20, 23) form an Isosceles triangle, because A ≡ B.
Values in the tuple (20, 20, 20) form an Equilateral triangle, because A ≡ B ≡ C.
Values in the tuple (20, 21, 22) form a Scalene triangle, because A ≠ B ≠ C.
Values in the tuple (13, 14, 30) cannot form a triangle because the combined value of sides A and B is not larger than that of side C.

Solution

SELECT CASE
    WHEN A + B > C AND A + C > B AND B + C > A THEN CASE
        WHEN A = B AND B = C THEN 'Equilateral'
        WHEN A = B OR A = C OR B = C THEN 'Isosceles'
        ELSE 'Scalene' END
    ELSE 'Not A Triangle' END
FROM TRIANGLES