정규표현식

regxone.com/lesson/introdution_abcs. >>> 연습사이트
regxr.com

 

Weather Observation Station 6
https://www.hackerrank.com/challenges/weather-observation-station-6/problem?h_r=internal-search

 

기존 풀이

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%'


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정규표현식 활용

SELECT DISTINCT city
FROM station
WHERE city REGEXP '^[aeiou].*'       >>> regular expression 
a,e,i,o,u 로 시작해야 하고, 그 뒤는 어떤 문자열이 와도 상관이 없음.


[aeiou] >>> a,e,i,o,u 중 어떤 문자중에 하나라도 들어가면
^문자열 시작위치 >>> 맨 앞
.* 임의의 문자열. = %
. >>> 어떤 문자열도 상관 없음
* >>> .이 몇번 반복될 것 인지?

 

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Weather Observation Station 7

https://www.hackerrank.com/challenges/weather-observation-station-7/problem?h_r=internal-search

SELECT DISTINCT city
FROM station
WHERE city REGEXP '.*[aeiouAEIOU]$'.  >>> ~로 끝나야 할떄 괄호 끝 $표시 >>> [~]$

 

 

Weather Observation Station 8

https://www.hackerrank.com/challenges/weather-observation-station-8/problem?h_r=internal-search

SELECT DISTINCT city
FROM station
WHERE city REGEXP '^[aeiouAEIOU].*[aeiouAEIOU]$' >>> 모음으로 시작하고 모음으로 끝나는 경우

 

Weather Observation Station 9
https://www.hackerrank.com/challenges/weather-observation-station-9/problem?h_r=internal-search

SELECT DISTINCT city
FROM station
WHERE city NOT REGEXP '^[aeiouAEIOU].*'.  >>> 모음으로 시작하지 않아야 할 때.  NOT 추가