오늘도 배운다

문제 source: LeetCode Write an SQL query to report the nth highest salary from the Employee table. If there is no nth highest salary, the query should report null. The query result format is in the following example. 제출답안(MySQL) CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT BEGIN RETURN ( SELECT DISTINCT(salary) FROM (SELECT id, salary, DENSE_RANK() OVER(ORDER BY salary DESC) AS ranking F..

문제 source: LeetCode 제출답안(MySQL) SELECT DISTINCT(l1.num) AS ConsecutiveNums FROM logs AS l1 JOIN logs AS l2 ON l1.id = l2.id+1 JOIN logs AS l3 ON l1.id = l3.id+2 WHERE l1.num = l2.num AND l1.num = l3.num 문제 바로가기(MySQL)

문제 source: LeetCode 제출답안(MySQL) SELECT score, DENSE_RANK() OVER(ORDER BY score DESC) AS 'rank' FROM scores 문제 바로가기(MySQL)

문제 source: HackerRank You are given a table, Projects, containing three columns: Task_ID, Start_Date and End_Date. It is guaranteed that the difference between the End_Date and the Start_Date is equal to 1 day for each row in the table. 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 co..

문제 source: HackerRank 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, and power of the wands that Ron's interested in, sorted in order of desce..

문제 source: HackerRank 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 challenges, then sort the result by hacker_id. If more than one student created the same..

문제 source: HackerRank You are given three tables: Students, Friends and Packages. Students contains two columns: ID and Name. Friends contains two columns: ID and Friend_ID (ID of the ONLY best friend). Packages contains two columns: ID and Salary (offered salary in $ thousands per month). Write a query to output the names of those students whose best friends got offered a higher salary than the..

Forecasts for Product Demand 데이터 조사 및 수집 데이터를 정제하기에 앞서 예측에 도움이 될 만한 데이터를 조사하고 수집하고자 함 수집할 데이터 1 공휴일 어느나라 공휴일 데이터를 모아야할까? 데이터셋의 출처에 관한 정보는 찾을 수 없다. 다만, Kaggle에 데이터셋을 올린 Felix Zhao는 중국인이며 그가 일하는 회사는 미국회사이다. 어느 국가인지 특정할 수 없으므로 중국, 미국 공휴일 데이터를 수집하였음 from holidays import country_holidays import pandas as pd class Holidays(): def __init__(self, ls_years): self.ls_years = ls_years # list of dataframe c..