[MySQL/HackerRank] Type of Triangle

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 (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.

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

 

▼ 잘못 작성한 나의 코드

Explanation에서 설명된 마지막 사항을 고려하지 못했다, 삼각형의 기본 조건.

SELECT
     CASE
        WHEN (A=B) AND (A=C) THEN 'Equilateral'
        WHEN (A=B) OR (A=C) OR (B=C) THEN 'Isosceles'
        WHEN (A<>B) AND (A<>C) AND (B<>C) THEN 'Scalene'
        ELSE 'Not A Triangle'
        END AS result
FROM
	TRIANGLES

 

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