SQL：无法理解CASE语法

-3

我试图解决的检测，对此我有以下代码三角类型Hackerrank问题：SQL：无法理解CASE语法

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;

但它不工作：

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

来源

2016-11-09 milos

你错误地使用'CASE'。你想达到什么目的？ –

大小写必须是select或where子句的一部分 – Jens

这不是它无法理解的语法，是您使用它的错误。在'FROM' – Lamak

不知道你打算做，但这应该工作：

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，第一，字符串必须用单引号包裹，双引号用于列名。其次，语法是：

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

来源

2016-11-09 14:01:54 sagi

只是澄清一点 - 单引号是用于分隔字符串的SQL标准，但MySQL确实支持双引号。对于列和表名称，它应该使用反引号而不是单引号。 – PaulF

我想你想你的输出是这样的：

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

等等...

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

来源

2016-11-09 14:01:55

SQL：无法理解CASE语法

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