[MySQL/HackerRank] Type of Triangle

Question

 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 3 sides of equal length.
• Isosceles: It's a triangle with 2 sides of equal length.
• Scalene: It's a triangle with 3 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  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.

My Answer

with tbl (a,b,c, max_v, min_v , med_v) as 
(
select a,b,c,
        greatest(a,b,c), 
        least(a,b,c), 
        a+b+c - (greatest(a,b,c) + least(a,b,c)) 
from triangles
)
select case when max_v = min_v then 'Equilateral'
            when max_v >= (med_v + min_v) then 'Not A Triangle'
            when (max_v = med_v) or (min_v = med_v) then 'Isosceles'
            else 'Scalene'
        end
from tbl

Result

Equilateral 
Equilateral 
Isosceles 
Equilateral 
Isosceles 
Equilateral 
Scalene 
Not A Triangle 
Scalene 
Scalene 
Scalene 
Not A Triangle 
Not A Triangle 
Scalene 
Equilateral

출처 : https://www.hackerrank.com/challenges/what-type-of-triangle/problem

Type of Triangle | HackerRank