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Database Practice

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#	Solution	Tags	Difficulty	Remark
0175	Combine Two Tables	Database	Easy
0176	Second Highest Salary	Database	Medium
0177	Nth Highest Salary	Database	Medium
0178	Rank Scores	Database	Medium
0180	Consecutive Numbers	Database	Medium
0181	Employees Earning More Than Their Managers	Database	Easy
0182	Duplicate Emails	Database	Easy
0183	Customers Who Never Order	Database	Easy
0184	Department Highest Salary	Database	Medium
0185	Department Top Three Salaries	Database	Hard
0196	Delete Duplicate Emails	Database	Easy
0197	Rising Temperature	Database	Easy
0262	Trips and Users	Database	Hard
0511	Game Play Analysis I	Database	Easy
0512	Game Play Analysis II	Database	Easy	????
0534	Game Play Analysis III	Database	Medium	????
0550	Game Play Analysis IV	Database	Medium
0569	Median Employee Salary	Database	Hard	????
0570	Managers with at Least 5 Direct Reports	Database	Medium
0571	Find Median Given Frequency of Numbers	Database	Hard	????
0574	Winning Candidate	Database	Medium	????
0577	Employee Bonus	Database	Easy
0578	Get Highest Answer Rate Question	Database	Medium	????
0579	Find Cumulative Salary of an Employee	Database	Hard	????
0580	Count Student Number in Departments	Database	Medium	????
0584	Find Customer Referee	Database	Easy
0585	Investments in 2016	Database	Medium
0586	Customer Placing the Largest Number of Orders	Database	Easy
0595	Big Countries	Database	Easy
0596	Classes More Than 5 Students	Database	Easy
0597	Friend Requests I Overall Acceptance Rate	Database	Easy	????
0601	Human Traffic of Stadium	Database	Hard
0602	Friend Requests II Who Has the Most Friends	Database	Medium
0603	Consecutive Available Seats	Database	Easy	????
0607	Sales Person	Database	Easy
0608	Tree Node	Database	Medium
0610	Triangle Judgement	Database	Easy
0612	Shortest Distance in a Plane	Database	Medium	????
0613	Shortest Distance in a Line	Database	Easy	????
0614	Second Degree Follower	Database	Medium	????
0615	Average Salary Departments VS Company	Database	Hard	????
0618	Students Report By Geography	Database	Hard	????
0619	Biggest Single Number	Database	Easy
0620	Not Boring Movies	Database	Easy
0626	Exchange Seats	Database	Medium
0627	Swap Salary	Database	Easy
1045	Customers Who Bought All Products	Database	Medium
1050	Actors and Directors Who Cooperated At Least Three Times	Database	Easy
1068	Product Sales Analysis I	Database	Easy
1069	Product Sales Analysis II	Database	Easy	????
1070	Product Sales Analysis III	Database	Medium
1075	Project Employees I	Database	Easy
1076	Project Employees II	Database	Easy	????
1077	Project Employees III	Database	Medium	????
1082	Sales Analysis I	Database	Easy	????
1083	Sales Analysis II	Database	Easy	????
1084	Sales Analysis III	Database	Easy
1097	Game Play Analysis V	Database	Hard	????
1098	Unpopular Books	Database	Medium	????
1107	New Users Daily Count	Database	Medium	????
1112	Highest Grade For Each Student	Database	Medium	????
1113	Reported Posts	Database	Easy	????
1126	Active Businesses	Database	Medium	????
1127	User Purchase Platform	Database	Hard	????
1132	Reported Posts II	Database	Medium	????
1141	User Activity for the Past 30 Days I	Database	Easy
1142	User Activity for the Past 30 Days II	Database	Easy	????
1148	Article Views I	Database	Easy
1149	Article Views II	Database	Medium	????
1158	Market Analysis I	Database	Medium
1159	Market Analysis II	Database	Hard	????
1164	Product Price at a Given Date	Database	Medium
1173	Immediate Food Delivery I	Database	Easy	????
1174	Immediate Food Delivery II	Database	Medium
1179	Reformat Department Table	Database	Easy
1193	Monthly Transactions I	Database	Medium
1194	Tournament Winners	Database	Hard	????
1204	Last Person to Fit in the Bus	Database	Medium
1205	Monthly Transactions II	Database	Medium	????
1211	Queries Quality and Percentage	Database	Easy
1212	Team Scores in Football Tournament	Database	Medium	????
1225	Report Contiguous Dates	Database	Hard	????
1241	Number of Comments per Post	Database	Easy	????
1251	Average Selling Price	Database	Easy
1264	Page Recommendations	Database	Medium	????
1270	All People Report to the Given Manager	Database	Medium	????
1280	Students and Examinations	Database	Easy
1285	Find the Start and End Number of Continuous Ranges	Database	Medium	????
1294	Weather Type in Each Country	Database	Easy	????
1303	Find the Team Size	Database	Easy	????
1308	Running Total for Different Genders	Database	Medium	????
1321	Restaurant Growth	Database	Medium
1322	Ads Performance	Database	Easy	????
1327	List the Products Ordered in a Period	Database	Easy
1336	Number of Transactions per Visit	Database	Hard	????
1341	Movie Rating	Database	Medium
1350	Students With Invalid Departments	Database	Easy	????
1355	Activity Participants	Database	Medium	????
1364	Number of Trusted Contacts of a Customer	Database	Medium	????
1369	Get the Second Most Recent Activity	Database	Hard	????
1378	Replace Employee ID With The Unique Identifier	Database	Easy
1384	Total Sales Amount by Year	Database	Hard	????
1393	Capital GainLoss	Database	Medium
1398	Customers Who Bought Products A and B but Not C	Database	Medium	????
1407	Top Travellers	Database	Easy
1412	Find the Quiet Students in All Exams	Database	Hard	????
1421	NPV Queries	Database	Easy	????
1435	Create a Session Bar Chart	Database	Easy	????
1440	Evaluate Boolean Expression	Database	Medium	????
1445	Apples & Oranges	Database	Medium	????
1454	Active Users	Database	Medium	????
1459	Rectangles Area	Database	Medium	????
1468	Calculate Salaries	Database	Medium	????
1479	Sales by Day of the Week	Database	Hard	????
1484	Group Sold Products By The Date	Database	Easy
1495	Friendly Movies Streamed Last Month	Database	Easy	????
1501	Countries You Can Safely Invest In	Database	Medium	????
1511	Customer Order Frequency	Database	Easy	????
1517	Find Users With Valid E-Mails	Database	Easy
1527	Patients With a Condition	Database	Easy
1532	The Most Recent Three Orders	Database	Medium	????
1543	Fix Product Name Format	Database	Easy	????
1549	The Most Recent Orders for Each Product	Database	Medium	????
1555	Bank Account Summary	Database	Medium	????
1565	Unique Orders and Customers Per Month	Database	Easy	????
1571	Warehouse Manager	Database	Easy	????
1581	Customer Who Visited but Did Not Make Any Transactions	Database	Easy
1587	Bank Account Summary II	Database	Easy
1596	The Most Frequently Ordered Products for Each Customer	Database	Medium	????
1607	Sellers With No Sales	Database	Easy	????
1613	Find the Missing IDs	Database	Medium	????
1623	All Valid Triplets That Can Represent a Country	Database	Easy	????
1633	Percentage of Users Attended a Contest	Database	Easy
1635	Hopper Company Queries I	Database	Hard	????
1645	Hopper Company Queries II	Database	Hard	????
1651	Hopper Company Queries III	Database	Hard	????
1661	Average Time of Process per Machine	Database	Easy
1667	Fix Names in a Table	Database	Easy
1677	Product's Worth Over Invoices	Database	Easy	????
1683	Invalid Tweets	Database	Easy
1693	Daily Leads and Partners	Database	Easy
1699	Number of Calls Between Two Persons	Database	Medium	????
1709	Biggest Window Between Visits	Database	Medium	????
1715	Count Apples and Oranges	Database	Medium	????
1729	Find Followers Count	Database	Easy
1731	The Number of Employees Which Report to Each Employee	Database	Easy
1741	Find Total Time Spent by Each Employee	Database	Easy
1747	Leetflex Banned Accounts	Database	Medium	????
1757	Recyclable and Low Fat Products	Database	Easy
1767	Find the Subtasks That Did Not Execute	Database	Hard	????
1777	Product's Price for Each Store	Database	Easy	????
1783	Grand Slam Titles	Database	Medium	????
1789	Primary Department for Each Employee	Database	Easy
1795	Rearrange Products Table	Database	Easy
1809	Ad-Free Sessions	Database	Easy	????
1811	Find Interview Candidates	Database	Medium	????
1821	Find Customers With Positive Revenue this Year	Database	Easy	????
1831	Maximum Transaction Each Day	Database	Medium	????
1841	League Statistics	Database	Medium	????
1843	Suspicious Bank Accounts	Database	Medium	????
1853	Convert Date Format	Database	Easy	????
1867	Orders With Maximum Quantity Above Average	Database	Medium	????
1873	Calculate Special Bonus	Database	Easy
1875	Group Employees of the Same Salary	Database	Medium	????
1890	The Latest Login in 2020	Database	Easy
1892	Page Recommendations II	Database	Hard	????
1907	Count Salary Categories	Database	Medium
1917	Leetcodify Friends Recommendations	Database	Hard	????
1919	Leetcodify Similar Friends	Database	Hard	????
1934	Confirmation Rate	Database	Medium
1939	Users That Actively Request Confirmation Messages	Database	Easy	????
1949	Strong Friendship	Database	Medium	????
1951	All the Pairs With the Maximum Number of Common Followers	Database	Medium	????
1965	Employees With Missing Information	Database	Easy
1972	First and Last Call On the Same Day	Database	Hard	????
1978	Employees Whose Manager Left the Company	Database	Easy
1988	Find Cutoff Score for Each School	Database	Medium	????
1990	Count the Number of Experiments	Database	Medium	????
2004	The Number of Seniors and Juniors to Join the Company	Database	Hard	????
2010	The Number of Seniors and Juniors to Join the Company II	Database	Hard	????
2020	Number of Accounts That Did Not Stream	Database	Medium	????
2026	Low-Quality Problems	Database	Easy	????
2041	Accepted Candidates From the Interviews	Database	Medium	????
2051	The Category of Each Member in the Store	Database	Medium	????
2066	Account Balance	Database	Medium	????
2072	The Winner University	Database	Easy	????
2082	The Number of Rich Customers	Database	Easy	????
2084	Drop Type 1 Orders for Customers With Type 0 Orders	Database	Medium	????
2112	The Airport With the Most Traffic	Database	Medium	????
2118	Build the Equation	Database	Hard	????
2142	The Number of Passengers in Each Bus I	Database	Medium	????
2153	The Number of Passengers in Each Bus II	Database	Hard	????
2159	Order Two Columns Independently	Database	Medium	????
2173	Longest Winning Streak	Database	Hard	????
2175	The Change in Global Rankings	Database	Medium	????
2199	Finding the Topic of Each Post	Database	Hard	????
2205	The Number of Users That Are Eligible for Discount	Database	Easy	????
2228	Users With Two Purchases Within Seven Days	Database	Medium	????
2230	The Users That Are Eligible for Discount	Database	Easy	????
2238	Number of Times a Driver Was a Passenger	Database	Medium	????
2252	Dynamic Pivoting of a Table	Database	Hard	????
2253	Dynamic Unpivoting of a Table	Database	Hard	????
2292	Products With Three or More Orders in Two Consecutive Years	Database	Medium	????
2298	Tasks Count in the Weekend	Database	Medium	????
2308	Arrange Table by Gender	Database	Medium	????
2314	The First Day of the Maximum Recorded Degree in Each City	Database	Medium	????
2324	Product Sales Analysis IV	Database	Medium	????
2329	Product Sales Analysis V	Database	Easy	????
2339	All the Matches of the League	Database	Easy	????
2346	Compute the Rank as a Percentage	Database	Medium	????
2356	Number of Unique Subjects Taught by Each Teacher	Database	Easy
2362	Generate the Invoice	Database	Hard	????
2372	Calculate the Influence of Each Salesperson	Database	Medium	????
2377	Sort the Olympic Table	Database	Easy	????
2388	Change Null Values in a Table to the Previous Value	Database	Medium	????
2394	Employees With Deductions	Database	Medium	????
2474	Customers With Strictly Increasing Purchases	Database	Hard	????
2480	Form a Chemical Bond	Database	Easy	????
2494	Merge Overlapping Events in the Same Hall	Database	Hard	????
2504	Concatenate the Name and the Profession	Database	Easy	????
2668	Find Latest Salaries	Database	Easy	????
2669	Count Artist Occurrences On Spotify Ranking List	Database	Easy	????
2686	Immediate Food Delivery III	Database	Medium	????
2687	Bikes Last Time Used	Database	Easy	????
2688	Find Active Users	Database	Medium	????
2701	Consecutive Transactions with Increasing Amounts	Database	Hard	????
2720	Popularity Percentage	Database	Hard	????
2738	Count Occurrences in Text	Database	Medium	????
2752	Customers with Maximum Number of Transactions on Consecutive Days	Database	Hard	????
2783	Flight Occupancy and Waitlist Analysis	Database	Medium	????
2793	Status of Flight Tickets		Hard	????
2820	Election Results		Medium	????
2837	Total Traveled Distance	Database	Easy	????
2853	Highest Salaries Difference	Database	Easy	????
2854	Rolling Average Steps	Database	Medium	????
2893	Calculate Orders Within Each Interval	Database	Medium	????
2922	Market Analysis III	Database	Medium	????
2978	Symmetric Coordinates	Database	Medium	????
2984	Find Peak Calling Hours for Each City	Database	Medium	????
2985	Calculate Compressed Mean	Database	Easy	????
2986	Find Third Transaction	Database	Medium	????
2987	Find Expensive Cities	Database	Easy	????
2988	Manager of the Largest Department	Database	Medium	????
2989	Class Performance	Database	Medium	????
2990	Loan Types	Database	Easy	????
2991	Top Three Wineries	Database	Hard	????
2993	Friday Purchases I	Database	Medium	????
2994	Friday Purchases II	Database	Hard	????
2995	Viewers Turned Streamers	Database	Hard	????
3050	Pizza Toppings Cost Analysis	Database	Medium	????
3051	Find Candidates for Data Scientist Position	Database	Easy	????
3052	Maximize Items	Database	Hard	????
3053	Classifying Triangles by Lengths	Database	Easy	????
3054	Binary Tree Nodes	Database	Medium	????
3055	Top Percentile Fraud	Database	Medium	????
3056	Snaps Analysis	Database	Medium	????
3057	Employees Project Allocation	Database	Hard	????
3058	Friends With No Mutual Friends	Database	Medium	????
3059	Find All Unique Email Domains	Database	Easy	????
3060	User Activities within Time Bounds	Database	Hard	????
3061	Calculate Trapping Rain Water	Database	Hard	????
3087	Find Trending Hashtags		Medium	????

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