inner join

SQL Project Planning | HackerRank Write a query to output the start and end dates of projects listed by the number of days it took to complete the project in ascending order. www.hackerrank.com Problem If the End_Date of the tasks are consecutive, then they are part of the same project. Samantha is interested in finding the total number of different projects completed. Write a query to output th..

African Cities | HackerRank Query the names of all cities on the continent 'Africa'. www.hackerrank.com Problem Given the CITY and COUNTRY tables, query the names of all cities where the CONTINENT is 'Africa'. Note: CITY.CountryCode and COUNTRY.Code are matching key columns. -> 아프리카 대륙에 있는 모든 도시의 이름을 출력하시오. Answer select a.name from city a inner join country b on a.countrycode = b.code where b.c..

Challenges | HackerRank Print the total number of challenges created by hackers. www.hackerrank.com Problem Julia asked her students to create some coding challenges. Write a query to print the hacker_id, name, and the total number of challenges created by each student. Sort your results by the total number of challenges in descending order. If more than one student created the same number of ch..

Population Census | HackerRank Query the sum of the populations of all cities on the continent 'Asia'. www.hackerrank.com Problem Given the CITY and COUNTRY tables, query the sum of the populations of all cities where the CONTINENT is 'Asia'. -> 아시아에 있는 모든 도시의 인구 수의 합을 출력하시오. Answer select sum(a.population) from city a inner join country b on a.countrycode = b.code where b.continent = "Asia"

Ollivander's Inventory | HackerRank Help pick out Ron's new wand. www.hackerrank.com Problem Harry Potter and his friends are at Ollivander's with Ron, finally replacing Charlie's old broken wand. Hermione decides the best way to choose is by determining the minimum number of gold galleons needed to buy each non-evil wand of high power and age. Write a query to print the id, age, coins_needed, a..