Question

我试图解决检测三角形类型的Hackerrank问题，我有以下代码：

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

但它不起作用：

ERROR 1064 (42000) at line 1: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CASE
        WHEN (A >= B + C) OR (B >= A + C) OR (C >= A + B) THEN "Not A Trian' at line 2

Answer 1

我想你想要你的输出：

A    B    C   TYPE
6    2    3   Not a Triangle
3    3    3   Equilater

依旧......

试试这个：

SELECT A,B,C, 
CASE
    WHEN (A >= B + C) OR (B >= A + C) OR (C >= A + B) THEN "Not A Triangle"
    WHEN A = B AND B = C THEN "Equilateral"
    WHEN (A = B AND B = C) OR (B = C AND C = A) OR (C = A AND A = B) THEN "Isosceles"
    ELSE "Scalene"
END AS type
FROM TRIANGLES

Answer 2

不确定您打算做什么，但这应该有效：

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

你有两个错误，首先，字符串需要用单引号包装，双引号用于列名。其次，语法是：

SELECT <columns>
FROM <Table>
WHERE <Filters>

SQL：无法理解CASE语法

2 个答案: