Database LeetCode Problems: All 249, With Python Solutions

Every problem in this library that LeetCode tags Database — 249 in total, 33 of them with a complete Python solution, a worked example and the time and space complexity of the approach.

249 problems
100 Easy
105 Medium
44 Hard

Database problems by difficulty

Showing the first 200 of 249 problems. Problems with a complete Python solution are listed first, then by ascending problem number.

Easy (86)

#	Problem	Difficulty	Topics
175	Combine Two Tables	Easy	Database
181	Employees Earning More Than Their Managers	Easy	Database
182	Duplicate Emails	Easy	Database
183	Customers Who Never Order	Easy	Database
196	Delete Duplicate Emails	Easy	Database
197	Rising Temperature	Easy	Database
511	Game Play Analysis I	Easy	Database
577	Employee Bonus	Easy	Database
584	Find Customer Referee	Easy	Database
586	Customer Placing the Largest Number of Orders	Easy	Database
595	Big Countries	Easy	Database
596	Classes With at Least 5 Students	Easy	Database
607	Sales Person	Easy	Database
610	Triangle Judgement	Easy	Database
619	Biggest Single Number	Easy	Database
620	Not Boring Movies	Easy	Database
627	Swap Sex of Employees	Easy	Database
1050	Actors and Directors Who Cooperated At Least Three Times	Easy	Database
1068	Product Sales Analysis I	Easy	Database
512	Game Play Analysis IIPremium	Easy	Database
597	Friend Requests I: Overall Acceptance RatePremium	Easy	Database
603	Consecutive Available SeatsPremium	Easy	Database
613	Shortest Distance in a LinePremium	Easy	Database
1069	Product Sales Analysis IIPremium	Easy	Database
1075	Project Employees I	Easy	Database
1076	Project Employees IIPremium	Easy	Database
1082	Sales Analysis IPremium	Easy	Database
1083	Sales Analysis IIPremium	Easy	Database
1084	Sales Analysis III	Easy	Database
1113	Reported PostsPremium	Easy	Database
1141	User Activity for the Past 30 Days I	Easy	Database
1142	User Activity for the Past 30 Days IIPremium	Easy	Database
1148	Article Views I	Easy	Database
1173	Immediate Food Delivery IPremium	Easy	Database
1179	Reformat Department Table	Easy	Database
1211	Queries Quality and Percentage	Easy	Database
1241	Number of Comments per PostPremium	Easy	Database
1251	Average Selling Price	Easy	Database
1280	Students and Examinations	Easy	Database
1294	Weather Type in Each CountryPremium	Easy	Database
1303	Find the Team SizePremium	Easy	Database
1322	Ads PerformancePremium	Easy	Database
1327	List the Products Ordered in a Period	Easy	Database
1350	Students With Invalid DepartmentsPremium	Easy	Database
1378	Replace Employee ID With The Unique Identifier	Easy	Database
1407	Top Travellers	Easy	Database
1421	NPV QueriesPremium	Easy	Database
1435	Create a Session Bar ChartPremium	Easy	Database
1484	Group Sold Products By The Date	Easy	Database
1495	Friendly Movies Streamed Last MonthPremium	Easy	Database
1511	Customer Order FrequencyPremium	Easy	Database
1517	Find Users With Valid E-Mails	Easy	Database
1527	Patients With a Condition	Easy	Database
1543	Fix Product Name FormatPremium	Easy	Database
1565	Unique Orders and Customers Per MonthPremium	Easy	Database
1571	Warehouse ManagerPremium	Easy	Database
1581	Customer Who Visited but Did Not Make Any Transactions	Easy	Database
1587	Bank Account Summary II	Easy	Database
1607	Sellers With No SalesPremium	Easy	Database
1623	All Valid Triplets That Can Represent a CountryPremium	Easy	Database
1633	Percentage of Users Attended a Contest	Easy	Database
1661	Average Time of Process per Machine	Easy	Database
1667	Fix Names in a Table	Easy	Database
1677	Product's Worth Over InvoicesPremium	Easy	Database
1683	Invalid Tweets	Easy	Database
1693	Daily Leads and Partners	Easy	Database
1729	Find Followers Count	Easy	Database
1731	The Number of Employees Which Report to Each Employee	Easy	Database
1741	Find Total Time Spent by Each Employee	Easy	Database
1757	Recyclable and Low Fat Products	Easy	Database
1777	Product's Price for Each StorePremium	Easy	Database
1789	Primary Department for Each Employee	Easy	Database
1795	Rearrange Products Table	Easy	Database
1809	Ad-Free SessionsPremium	Easy	Database
1821	Find Customers With Positive Revenue this YearPremium	Easy	Database
1853	Convert Date FormatPremium	Easy	Database
1873	Calculate Special Bonus	Easy	Database
1890	The Latest Login in 2020	Easy	Database
1939	Users That Actively Request Confirmation MessagesPremium	Easy	Database
1965	Employees With Missing Information	Easy	Database
1978	Employees Whose Manager Left the Company	Easy	Database
2026	Low-Quality ProblemsPremium	Easy	Database
2072	The Winner UniversityPremium	Easy	Database
2082	The Number of Rich CustomersPremium	Easy	Database
2205	The Number of Users That Are Eligible for DiscountPremium	Easy	Database
2230	The Users That Are Eligible for DiscountPremium	Easy	Database

Medium (82)

#	Problem	Difficulty	Topics
176	Second Highest Salary	Medium	Database
177	Nth Highest Salary	Medium	Database
178	Rank Scores	Medium	Database
180	Consecutive Numbers	Medium	Database
184	Department Highest Salary	Medium	Database
550	Game Play Analysis IV	Medium	Database
570	Managers with at Least 5 Direct Reports	Medium	Database
585	Investments in 2016	Medium	Database
602	Friend Requests II: Who Has the Most Friends	Medium	Database
608	Tree Node	Medium	Database
626	Exchange Seats	Medium	Database
534	Game Play Analysis IIIPremium	Medium	Database
574	Winning CandidatePremium	Medium	Database
578	Get Highest Answer Rate QuestionPremium	Medium	Database
580	Count Student Number in DepartmentsPremium	Medium	Database
612	Shortest Distance in a PlanePremium	Medium	Database
614	Second Degree FollowerPremium	Medium	Database
1045	Customers Who Bought All Products	Medium	Database
1070	Product Sales Analysis III	Medium	Database
1077	Project Employees IIIPremium	Medium	Database
1098	Unpopular BooksPremium	Medium	Database
1107	New Users Daily CountPremium	Medium	Database
1112	Highest Grade For Each StudentPremium	Medium	Database
1126	Active BusinessesPremium	Medium	Database
1132	Reported Posts IIPremium	Medium	Database
1149	Article Views IIPremium	Medium	Database
1158	Market Analysis I	Medium	Database
1164	Product Price at a Given Date	Medium	Database
1174	Immediate Food Delivery II	Medium	Database
1193	Monthly Transactions I	Medium	Database
1204	Last Person to Fit in the Bus	Medium	Database
1205	Monthly Transactions IIPremium	Medium	Database
1212	Team Scores in Football TournamentPremium	Medium	Database
1264	Page RecommendationsPremium	Medium	Database
1270	All People Report to the Given ManagerPremium	Medium	Database
1285	Find the Start and End Number of Continuous RangesPremium	Medium	Database
1308	Running Total for Different GendersPremium	Medium	Database
1321	Restaurant Growth	Medium	Database
1341	Movie Rating	Medium	Database
1355	Activity ParticipantsPremium	Medium	Database
1364	Number of Trusted Contacts of a CustomerPremium	Medium	Database
1393	Capital Gain/Loss	Medium	Database
1398	Customers Who Bought Products A and B but Not CPremium	Medium	Database
1440	Evaluate Boolean ExpressionPremium	Medium	Database
1445	Apples & OrangesPremium	Medium	Database
1454	Active UsersPremium	Medium	Database
1459	Rectangles AreaPremium	Medium	Database
1468	Calculate SalariesPremium	Medium	Database
1501	Countries You Can Safely Invest InPremium	Medium	Database
1532	The Most Recent Three OrdersPremium	Medium	Database
1549	The Most Recent Orders for Each ProductPremium	Medium	Database
1555	Bank Account SummaryPremium	Medium	Database
1596	The Most Frequently Ordered Products for Each CustomerPremium	Medium	Database
1613	Find the Missing IDsPremium	Medium	Database
1699	Number of Calls Between Two PersonsPremium	Medium	Database
1709	Biggest Window Between VisitsPremium	Medium	Database
1715	Count Apples and OrangesPremium	Medium	Database
1747	Leetflex Banned AccountsPremium	Medium	Database
1783	Grand Slam TitlesPremium	Medium	Database
1811	Find Interview CandidatesPremium	Medium	Database
1831	Maximum Transaction Each DayPremium	Medium	Database
1841	League StatisticsPremium	Medium	Database
1843	Suspicious Bank AccountsPremium	Medium	Database
1867	Orders With Maximum Quantity Above AveragePremium	Medium	Database
1875	Group Employees of the Same SalaryPremium	Medium	Database
1907	Count Salary Categories	Medium	Database
1934	Confirmation Rate	Medium	Database
1949	Strong FriendshipPremium	Medium	Database
1951	All the Pairs With the Maximum Number of Common FollowersPremium	Medium	Database
1988	Find Cutoff Score for Each SchoolPremium	Medium	Database
1990	Count the Number of ExperimentsPremium	Medium	Database
2020	Number of Accounts That Did Not StreamPremium	Medium	Database
2041	Accepted Candidates From the InterviewsPremium	Medium	Database
2051	The Category of Each Member in the StorePremium	Medium	Database
2066	Account BalancePremium	Medium	Database
2084	Drop Type 1 Orders for Customers With Type 0 OrdersPremium	Medium	Database
2112	The Airport With the Most TrafficPremium	Medium	Database
2142	The Number of Passengers in Each Bus IPremium	Medium	Database
2159	Order Two Columns IndependentlyPremium	Medium	Database
2175	The Change in Global RankingsPremium	Medium	Database
2228	Users With Two Purchases Within Seven DaysPremium	Medium	Database
2238	Number of Times a Driver Was a PassengerPremium	Medium	Database

Hard (32)

#	Problem	Difficulty	Topics
185	Department Top Three Salaries	Hard	Database
262	Trips and Users	Hard	Database
601	Human Traffic of Stadium	Hard	Database
569	Median Employee SalaryPremium	Hard	Database
571	Find Median Given Frequency of NumbersPremium	Hard	Database
579	Find Cumulative Salary of an EmployeePremium	Hard	Database
615	Average Salary: Departments VS CompanyPremium	Hard	Database
618	Students Report By GeographyPremium	Hard	Database
1097	Game Play Analysis VPremium	Hard	Database
1127	User Purchase PlatformPremium	Hard	Database
1159	Market Analysis IIPremium	Hard	Database
1194	Tournament WinnersPremium	Hard	Database
1225	Report Contiguous DatesPremium	Hard	Database
1336	Number of Transactions per VisitPremium	Hard	Database
1369	Get the Second Most Recent ActivityPremium	Hard	Database
1384	Total Sales Amount by YearPremium	Hard	Database
1412	Find the Quiet Students in All ExamsPremium	Hard	Database
1479	Sales by Day of the WeekPremium	Hard	Database
1635	Hopper Company Queries IPremium	Hard	Database
1645	Hopper Company Queries IIPremium	Hard	Database
1651	Hopper Company Queries IIIPremium	Hard	Database
1767	Find the Subtasks That Did Not ExecutePremium	Hard	Database
1892	Page Recommendations IIPremium	Hard	Database
1917	Leetcodify Friends RecommendationsPremium	Hard	Database
1919	Leetcodify Similar FriendsPremium	Hard	Database
1972	First and Last Call On the Same DayPremium	Hard	Database
2004	The Number of Seniors and Juniors to Join the CompanyPremium	Hard	Database
2010	The Number of Seniors and Juniors to Join the Company IIPremium	Hard	Database
2118	Build the EquationPremium	Hard	Database
2153	The Number of Passengers in Each Bus IIPremium	Hard	Database
2173	Longest Winning StreakPremium	Hard	Database
2199	Finding the Topic of Each PostPremium	Hard	Database

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