mysql - MySQL中的三角形类型

Question

问题陈述:

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:

• Not A Triangle: The given values of A, B, and C don't form a triangle.
• 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. 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
------------
A  B  C
20 20 23
20 20 20
20 21 22
13 14 30

Sample Output
-------------
Isosceles
Equilateral
Scalene
Not A Triangle

失败的尝试:

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 A=C or B=C then "Isosceles"
        when A<>B and B<>C then "Scalene"

    end as triangles_type
    from TRIANGLES;

Answer 1

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 A = C or B = C THEN 'Isosceles'
    WHEN A <> B and B <> C THEN 'Scalene'
  END tuple
FROM TRIANGLES;

1. 通过使用 case 语句，检查给定的输入是否为三角形。
2. 如果是三角形，则检查所有边是否相同。如果 true 三角形类型为“等边”。
3. 如果不是，则检查是否有任何两条边相等。如果 true，则三角形类型为“等腰”
4. 在不相等的情况下，三角形类型的任何边都是'Scalene'。我们也可以直接使用ELSE。