Prepare > SQL > Advanced Select > Type of Triangle

Type of Triangle | HackerRank

 

문제

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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.

 

 

 

 

코드

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

FROM TRIANGLES;

 

 

 

 

노트

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항 비교연산은 두 개씩만 할 수 있음

A+B > C AND B+C > A AND C+A > B
A=B AND B=C
A=B OR B=C OR C=A

• A = B = C같은거 안됨

 

 

CASE WHEN ~ THEN ~ END는 중첩 가능

 

두 번째 시도

SELECT IF((A >= B+C) or (B >= A+C) or (C >= A+B), 'Not A Triangle',
    CASE
        WHEN A=B AND B=C THEN 'Equilateral'
        WHEN A=B OR C=B OR C=A THEN 'Isosceles'
        ELSE 'Scalene' END
)
FROM TRIANGLES;

• IF(조건, 참일 경우, 거짓일 경우)
• 조건을 차례로 필터링