# About This Book ### Introduction This book provides questions about Database Hard Level on Leetcod and Hive SQL answers. (There are 28 questions in total) Hard level tests the ability of flexible ideas and require familiarity with the following : * Various Hive SQL functions, including Mathematical functions, data functions, string functions... * Multi-table join, including subquery, JOIN, UNION * Windows function I strongly recommend that each question must be considered in-depth, and running Query to view the output results. **Do not** look at the answers directly, otherwise, it will reduce the learning effect. In addition, the idea of solving the problem is not unique, so the answer is for reference only. 這本書提供Leetcod上 Database Hard Level的題目及Hive SQL解答，一共28題 Hard Level很考驗綜合運用的能力，你要具備靈活的思路以及熟悉以下查詢用法： * 各種函數的運用 * 多表連結，包含子查詢、JOIN、UNION * Windows function 即是能高度掌握<入門數據分析 掌握Hive SQL取數能力>課程所有內容 > 本課程已上架Hahow平台，如您對課程有興趣，可點擊[此鏈結](https://hahow.in/cr/andyrockhive)查看課程詳細說明 強烈建議每道題目需經過思考，若一時無法想出一步到位的Query，可先運行片段的Query查看輸出結果，與題目希望的result對比，再思考差異及延伸Query，勿直接看答案，否則學習效果將打(骨)折。 另外，解題思路並不唯一，故答案僅供參考。 ### About leetcode SQL question * [Leetcode](https://leetcode.com/) is one of the most well-known online judge platforms that you can use to practice your programming skills by solving coding questions * Enter the Problem page and filter the topic of Database, here are all SQL questions. * Problems are three difficulty levels (Easy, Medium, and Hard) , most of the questions need to be paid to unlock. ![](https://tva1.sinaimg.cn/large/008i3skNgy1gx6fffc6koj31dc0u0wjo.jpg) ### Hard Problems This is a list of [LeetCode's Hard Level Database problems](https://leetcode.com/problemset/database/?difficulty=HARD\&page=1) and solutions with Hive SQL. My online course in Hahow platform provides the big data environment and *HUE* (Hue is a Web interface for analyzing data with *Apache Hadoop*), you can create a database (such as leetcode) to store the data for each exercises. ```sql create database if not exists leetcode ; ```
exercise idexercise_name
1185. Department Top Three Salaries
2262. Trips and Users
3569.Median Employee Salary
4571.Find Median Given Frequency of Numbers
5579.Find Cumulative Salary Of An Employee Problem
6601.Human Traffic of Stadium
7615.Average Salary: Departments VS Company
8618. Students Report By Geography
91097. Game Play Analysis V
101127. User Purchase Platform
111159. Market Analysis II
121194. Tournament Winners
131225.Report Contiguous Dates
141336.The number of transactions per visit
151369.Get The Second Most Recent Activity Proble
161384. Total Sales Amount by Year
171412.Find the Quiet Students in All Exams
181479. Sales by Day of the Week
191635. Hopper Company Queries I
201645. Hopper Company Queries II
211651. Hopper Company Queries III
221767.Find the Subtasks That Did Not Execute
231892.Page Recommendations II
241917.Leetcodify Friends Recommendations
251919.Leetcodify Similar Friends
261972.First and Last Call On the Same Day
272004.The Number of Seniors and Juniors to Join the Company
282010.The Number of Seniors and Juniors to Join the Company II