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

A + B <= C OR B + C <= A OR C + A <= B THEN 'Not A Triangle' 조건이

A = B OR B = C OR C = A THEN 'Isosceles' 조건보다 먼저 나와야 하는 이유

A = B OR B = C OR C = A THEN 'Isosceles 조건이 먼저 나오게 되면

A = B = 1이고 C = 2인 경우 삼각형 조건이 성립하지 않지만,

Isosceles(이등변 삼각형)라는 값을 RETURN하기 때문이다.

해커랭크 Type of Triangle SQL

SELECT DISTINCT CITY
  FROM STATION
 WHERE (CITY LIKE 'a%' OR
        CITY LIKE 'e%' OR
        CITY LIKE 'i%' OR
        CITY LIKE 'o%' OR
        CITY LIKE 'u%')

a로 시작하는 문자열을 검색 : 'a%'

a로 시작하는 3글자의 문자열 검색 : 'a__'

SELECT DISTINCT CITY
  FROM STATION
 WHERE CITY REGEXP '^[aeiou]'

정규 표현식 REGEXP : LIKE보다 복잡한 문자열 조건으로 검색 가능

^[aeiou] : a 또는 e 또는 i 또는 o 또는 u로 시작하는 문자열

SELECT DISTINCT CITY
  FROM STATION
 WHERE (CITY LIKE '%a' OR
        CITY LIKE '%e' OR
        CITY LIKE '%i' OR
        CITY LIKE '%o' OR
        CITY LIKE '%u')

SELECT DISTINCT CITY
  FROM STATION
 WHERE CITY REGEXP '[aeiou]$'

[aeiou]$ : a 또는 e 또는 i 또는 o 또는 u로 끝나는 문자열

해커랭크 Weather Observation Station SQL

(SELECT CITY, LENGTH(CITY)
   FROM STATION
  WHERE LENGTH(CITY) = (SELECT MIN(LENGTH(CITY)) FROM STATION)
  ORDER BY CITY
  LIMIT 1)
UNION ALL
(SELECT CITY, LENGTH(CITY)
   FROM STATION
  WHERE LENGTH(CITY) = (SELECT MAX(LENGTH(CITY)) FROM STATION)
  ORDER BY CITY
  LIMIT 1)

(SELECT CITY, LENGTH(CITY)
   FROM STATION
  ORDER BY LENGTH(CITY) ASC, CITY ASC
  LIMIT 1);
(SELECT CITY, LENGTH(CITY)
   FROM STATION
  ORDER BY LENGTH(CITY) DESC, CITY ASC
  LIMIT 1)

UNION ALL을 쓰지 않고 세미콜론(;)으로 이어줘도 된다.

해커랭크 Weather Observation Station SQL