1. Weather Observation Station 3 https://www.hackerrank.com/challenges/weather-observation-station-3/problem?isFullScreen=true Weather Observation Station 3 | HackerRankQuery a list of unique CITY names with even ID numbers.www.hackerrank.com/*짝수인 id number를 가지는 시티 네임, 중복 제외짝수는 2로 나눠지는거*/SELECt DISTINCT cityFROM stationWHERE id % 2 = 0 ↓ where절에 이렇게도 쓸 수 있음SELECt DISTINCT cityFROM stationWHERE M..
숫자를 다루는 함수ROUND(칼럼명/값, n): 값을 소수점 이하 n자릿수로 반올림TRUNCATE(칼럼명/값, n): 값을 소수점 이하 n자릿수까지 남기고 나머지 버림CEIL(칼럼명/값): 값의 소수점 이하를 올림해 정수 반환FLOOR(칼럼명/값): 값의 소수점 이하를 버림해 정수 반환 POWER(칼럼명/값, n) = POW(칼럼명/값, n): 값을 n제곱해서 반환 >> POWER(2, 3) = 8SQRT(칼럼명/값): 값의 제곱근을 반 >> SQRT(4) = 2*값의 n제곱근을 구하기 = 값의 1/n제곱을 구하기 = POWER(칼럼명/값, 1/n)>> POWER(8, 1/3) = 2 MOD(칼럼명/값, n) : 값을 n으로 나눴을 때 나머지를 반환 >> 칼럼명/값 % n >> MOD(5, 2) = 1A..
sql 코테 대비.. 전에 공부하면서 풀었던 문제 제외 1. https://www.hackerrank.com/challenges/weather-observation-station-9/problem?isFullScreen=true Weather Observation Station 9 | HackerRank Query an alphabetically ordered list of CITY names not starting with vowels. www.hackerrank.com Q: Query the list of CITY names from STATION that do not start with vowels. Your result cannot contain duplicates. Input Format The..
COUNT 개수를 세어줌 SELECT COUNT(* 또는 칼럼명) FROM 테이블명 Products ProductID ProductName SupplierID Price 1 A 1 18 2 A 2 19 3 B 3 Null 4 C 5 22 5 Null Null 5 - 전체 개수 세기 SELECT COUNT (*) FROM products >> 5 - ProductName 개수 세기, 유일값만 세기 SELECT COUNT(productname) FROM products >> 4 -- Null 값은 빼고 세줌 SELECT COUNT(DISTINCT productname) FROM products >> 3 -- Null값 빼고 중복 안되게 SUM 숫자 데이터를 가진 칼럼의 합을 계산해줌 SELECT SUM(칼럼..
1. https://www.hackerrank.com/challenges/weather-observation-station-7/problem?isFullScreen=true Weather Observation Station 7 | HackerRank Query the list of CITY names ending with vowels (a, e, i, o, u) from STATION. www.hackerrank.com Q: Query the list of CITY names ending with vowels (a, e, i, o, u) from STATION. Your result cannot contain duplicates. Input Format The STATION table is describ..
1. https://www.hackerrank.com/challenges/revising-the-select-query-2/problem?isFullScreen=true Revising the Select Query II | HackerRank Query the city names for all American cities with populations larger than 120,000. www.hackerrank.com Q: Query the NAME field for all American cities in the CITY table with populations larger than 120000. The CountryCode for America is USA. The CITY table is de..
