SQL | HackerRank 삼각형 분류하기: 조건문 CASE를 활용한 다중 조건 처리

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.

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 a = c then 'Equilateral'
        when a = b or b = c or a = c then 'Isosceles'
        else 'Scalene'
    end as triangle_type
from triangles;

• 삼각형 조건: 세 변의 합 조건을 먼저 확인해야 하므로 가장 앞에 둡니다.
• (삼각형이 아니면 이후 분류는 무의미)
• A = B AND B = C: 세 변이 모두 같으면 Equilateral
• A = B OR B = C OR A = C: 두 변만 같으면 Isosceles
• 나머지는 Scalene