HAZEL

1] Weather Observation Station 3 >> 문제 Query a list of CITY names from STATION for cities that have an even ID number. Print the results in any order, but exclude duplicates from the answer. The STATION table is described as follows: where LAT_N is the northern latitude and LONG_W is the western longitude. >> 문제 푼 코드 SELECT distinct city FROM STATION WHERE id % 2 = 0 www.hackerrank.com/challenge..

Top Competitors >> 문제 Julia just finished conducting a coding contest, and she needs your help assembling the leaderboard! Write a query to print the respective hacker_id and name of hackers who achieved full scores for more than one challenge. Order your output in descending order by the total number of challenges in which the hacker earned a full score. If more than one hacker received full sc..

1] Population Density Difference >> 문제 Query the difference between the maximum and minimum populations in CITY. Input Format The CITY table is described as follows: >> 문제 푼 코드 select max(population) - min(population) from city www.hackerrank.com/challenges/population-density-difference/problem Population Density Difference | HackerRank Query the difference between the maximum and minimum city p..

New Companies >> 문제 Amber's conglomerate corporation just acquired some new companies. Each of the companies follows this hierarchy: Given the table schemas below, write a query to print the company_code, founder name, total number of lead managers, total number of senior managers, total number of managers, and total number of employees. Order your output by ascending company_code. Note: The tab..

1] Japan Population >> 문제 Query the sum of the populations for all Japanese cities in CITY. The COUNTRYCODE for Japan is JPN. Input Format The CITY table is described as follows: >> 문제해결 코드 SELECT SUM(POPULATION) from CITY WHERE COUNTRYCODE = 'JPN' www.hackerrank.com/challenges/japan-population/problem Japan Population | HackerRank Query to the sum of the populations of all Japanese cities in CI..

1] 182. Duplicate Emails >> 문제 Write a SQL query to find all duplicate emails in a table named Person. +----+---------+ | Id | Email | +----+---------+ | 1 | a@b.com | | 2 | c@d.com | | 3 | a@b.com | +----+---------+ For example, your query should return the following for the above table: +---------+ | Email | +---------+ | a@b.com | +---------+ >> 문제 해결 코드 select Email from person group by Emai..

1] 595. Big Countries >> 문제 There is a table World +-----------------+------------+------------+--------------+---------------+ | name | continent | area | population | gdp | +-----------------+------------+------------+--------------+---------------+ | Afghanistan | Asia | 652230 | 25500100 | 20343000 | | Albania | Europe | 28748 | 2831741 | 12960000 | | Algeria | Africa | 2381741 | 37100000 | ..

1. Symmetric Pairs >> 문제 You are given a table, Functions, containing two columns: X and Y. Two pairs (X1, Y1) and (X2, Y2) are said to be symmetric pairs if X1 = Y2 and X2 = Y1. Write a query to output all such symmetric pairs in ascending order by the value of X. List the rows such that X1 ≤ Y1. Sample Input Sample Output 20 20 20 21 22 23 >> 문제 풀이 SELECT X , Y FROM Functions WHERE X = Y GROUP..

1. 181. Employees Earning More Than Their Managers >> 문제 The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id. +----+-------+--------+-----------+ | Id | Name | Salary | ManagerId | +----+-------+--------+-----------+ | 1 | Joe | 70000 | 3 | | 2 | Henry | 80000 | 4 | | 3 | Sam | 60000 | NULL | | 4 | Max | 90000 |..

1. 183. Customers Who Never Order >> 문제 Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything. Table: Customers. +----+-------+ | Id | Name | +----+-------+ | 1 | Joe | | 2 | Henry | | 3 | Sam | | 4 | Max | +----+-------+ Table: Orders. +----+------------+ | Id | CustomerId | +----+------------+ | 1 ..