SQL Interview Questions

Relational queries and aggregation.

341 problems

#	Title	Difficulty	Topics
175	Combine Two Tables	Easy	sql
176	Second Highest Salary	Easy	sql
177	Nth Highest Salary	Medium	sql
178	Rank Scores	Medium	sql
180	Consecutive Numbers	Medium	sql
181	Employees Earning More Than Their Managers	Easy	sql
182	Duplicate Emails	Easy	sql
183	Customers Who Never Order	Easy	sql
184	Department Highest Salary	Medium	sql
185	Department Top Three Salaries	Hard	sql
192	Word Frequency	Medium	sql
193	Valid Phone Numbers	Easy	sql
194	Transpose File	Medium	sql
195	Tenth Line	Easy	sql
196	Delete Duplicate Emails	Easy	sql
197	Rising Temperature	Easy	sql
262	Trips and Users	Hard	sql
511	Game Play Analysis I	Easy	sql
512	Game Play Analysis II	Easy	sql
534	Game Play Analysis III	Medium	sql
550	Game Play Analysis IV	Medium	sql
569	Median Employee Salary	Hard	sql
570	Managers with at Least 5 Direct Reports	Medium	sql
571	Find Median Given Frequency of Numbers	Hard	sql
574	Winning Candidate	Medium	sql
577	Employee Bonus	Easy	sql
578	Get Highest Answer Rate Question	Medium	sql
579	Find Cumulative Salary of an Employee	Hard	sql
580	Count Student Number in Departments	Medium	sql
584	Find Customer Referee	Easy	sql
585	Investments in 2016	Medium	sql
586	Customer Placing the Largest Number of Orders	Easy	sql
595	Big Countries	Easy	sql
596	Classes More Than 5 Students	Easy	sql
597	Friend Requests I: Overall Acceptance Rate	Easy	sql
601	Human Traffic of Stadium	Hard	sql
602	Friend Requests II: Who Has the Most Friends	Medium	sql
603	Consecutive Available Seats	Easy	sql
607	Sales Person	Easy	sql
608	Tree Node	Medium	sql
610	Triangle Judgement	Easy	sql
612	Shortest Distance in a Plane	Medium	sql
613	Shortest Distance in a Line	Easy	sql
614	Second Degree Follower	Medium	sql
615	Average Salary: Departments VS Company	Hard	sql
618	Students Report By Geography	Hard	sql
619	Biggest Single Number	Easy	sql
620	Not Boring Movies	Easy	sql
626	Exchange Seats	Medium	sql
627	Swap Salary	Easy	sql
1045	Customers Who Bought All Products	Medium	sql
1050	Actors and Directors Who Cooperated At Least Three Times	Easy	sql
1068	Product Sales Analysis I	Easy	sql
1069	Product Sales Analysis II	Easy	sql
1070	Product Sales Analysis III	Medium	sql
1075	Project Employees I	Easy	sql
1076	Project Employees II	Easy	sql
1077	Project Employees III	Medium	sql
1082	Sales Analysis I	Easy	sql
1083	Sales Analysis II	Easy	sql
1084	Sales Analysis III	Easy	sql
1097	Game Play Analysis V	Hard	sql
1098	Unpopular Books	Medium	sql
1107	New Users Daily Count	Medium	sql
1112	Highest Grade For Each Student	Medium	sql
1113	Reported Posts	Easy	sql
1126	Active Businesses	Medium	sql
1127	User Purchase Platform	Hard	sql
1132	Reported Posts II	Medium	sql
1141	User Activity for the Past 30 Days I	Easy	sql
1142	User Activity for the Past 30 Days II	Easy	sql
1148	Article Views I	Easy	sql
1149	Article Views II	Medium	sql
1158	Market Analysis I	Medium	sql
1159	Market Analysis II	Hard	sql
1164	Product Price at a Given Date	Medium	sql
1173	Immediate Food Delivery I	Easy	sql
1174	Immediate Food Delivery II	Medium	sql
1179	Reformat Department Table	Easy	sql
1193	Monthly Transactions I	Medium	sql
1194	Tournament Winners	Hard	sql
1204	Last Person to Fit in the Elevator	Medium	sql
1205	Monthly Transactions II	Medium	sql
1211	Queries Quality and Percentage	Easy	sql
1212	Team Scores in Football Tournament	Medium	sql
1225	Report Contiguous Dates	Hard	sql
1241	Number of Comments per Post	Easy	sql
1251	Average Selling Price	Easy	sql
1264	Page Recommendations	Medium	sql
1270	All People Report to the Given Manager	Medium	sql
1280	Students and Examinations	Easy	sql
1285	Find the Start and End Number of Continuous Ranges	Medium	sql
1294	Weather Type in Each Country	Easy	sql
1303	Find the Team Size	Easy	sql
1308	Running Total for Different Genders	Medium	sql
1321	Restaurant Growth	Medium	sql
1322	Ads Performance	Easy	sql
1327	List the Products Ordered in a Period	Easy	sql
1336	Number of Transactions per Visit	Medium	sql
1341	Movie Rating	Medium	sql
1350	Students With Invalid Departments	Easy	sql
1355	Activity Participants	Medium	sql
1364	Number of Trusted Contacts of a Customer	Medium	sql
1369	Get the Second Most Recent Activity	Hard	sql
1378	Replace Employee ID With The Unique Identifier	Easy	sql
1384	Total Sales Amount by Year	Hard	sql
1393	Capital Gain/Loss	Medium	sql
1398	Customers Who Bought Products A and B but Not C	Medium	sql
1407	Top Travellers	Easy	sql
1412	Find the Quiet Students in All Exams	Hard	sql
1421	NPV Queries	Medium	sql
1435	Create a Session Bar Chart	Easy	sql
1440	Evaluate Boolean Expression	Medium	sql
1445	Apples & Oranges	Medium	sql
1454	Active Users	Medium	sql
1459	Rectangles Area	Medium	sql
1468	Calculate Salaries	Easy	sql
1479	Sales by Day of the Week	Hard	sql
1484	Group Sold Products By The Date	Easy	sql
1495	Friendly Movies Streamed Last Month	Easy	sql
1501	Countries You Can Safely Invest In	Medium	sql
1511	Customer Order Frequency	Easy	sql
1517	Find Users With Valid E-Mails	Easy	sql
1527	Patients With a Condition	Easy	sql
1532	The Most Recent Three Orders	Medium	sql
1543	Fix Product Name Format	Easy	sql
1549	The Most Recent Orders for Each Product	Medium	sql
1555	Bank Account Summary	Medium	sql
1565	Unique Orders and Customers Per Month	Easy	sql
1571	Warehouse Manager	Medium	sql
1581	Customer Who Visited but Did Not Make Any Transactions	Easy	sql
1587	Bank Account Summary II	Easy	sql
1596	The Most Frequently Ordered Products for Each Customer	Medium	sql
1607	Sellers With No Sales	Medium	sql
1613	Find the Missing IDs	Medium	sql
1623	All Valid Triplets That Can Represent a Country	Easy	sql
1633	Percentage of Users Attended a Contest	Easy	sql
1635	Hopper Company Queries I	Hard	sql
1645	Hopper Company Queries II	Hard	sql
1651	Hopper Company Queries III	Hard	sql
1661	Average Time of Process per Machine	Easy	sql
1667	Fix Names in a Table	Easy	sql
1677	Product's Worth Over Invoices	Easy	sql
1683	Invalid Tweets	Easy	sql
1693	Daily Leads and Partners	Easy	sql
1699	Number of Calls Between Two Persons	Medium	sql
1709	Biggest Window Between Visits	Medium	sql
1715	Count Apples and Oranges	Medium	sql
1729	Find Followers Count	Easy	sql
1731	The Number of Employees Which Report to Each Employee	Easy	sql
1741	Find Total Time Spent by Each Employee	Easy	sql
1747	Leetflex Banned Accounts	Medium	sql
1757	Recyclable and Low Fat Products	Easy	sql
1767	Find the Subtasks That Did Not Execute	Hard	sql
1777	Product's Price for Each Store	Easy	sql
1783	Grand Slam Titles	Medium	sql
1789	Primary Department for Each Employee	Easy	sql
1795	Rearrange Products Table	Easy	sql
1809	Ad-Free Sessions	Easy	sql
1811	Find Interview Candidates	Medium	sql
1821	Find Customers With Positive Revenue this Year	Easy	sql
1831	Maximum Transaction Each Day	Medium	sql
1841	League Statistics	Medium	sql
1843	Suspicious Bank Accounts	Medium	sql
1853	Convert Date Format	Easy	sql
1867	Orders With Maximum Quantity Above Average	Easy	sql
1873	Calculate Special Bonus	Easy	sql
1875	Group Employees of the Same Salary	Medium	sql
1890	The Latest Login in 2020	Easy	sql
1892	Page Recommendations II	Hard	sql
1907	Count Salary Categories	Medium	sql
1917	Leetcodify Friends Recommendations	Hard	sql
1919	Leetcodify Similar Friends	Hard	sql
1934	Confirmation Rate	Medium	sql
1939	Users That Actively Request Confirmation Messages	Easy	sql
1949	Strong Friendship	Medium	sql
1951	All the Pairs With the Maximum Number of Common Followers	Medium	sql
1965	Employees With Missing Information	Easy	sql
1972	First and Last Call On the Same Day	Hard	sql
1978	Employees Whose Manager Left the Company	Easy	sql
1988	Find Cutoff Score for Each School	Medium	sql
1990	Count the Number of Experiments	Easy	sql
2004	The Number of Seniors and Juniors to Join the Company	Hard	sql
2020	Number of Accounts That Did Not Stream	Medium	sql
2026	Low-Quality Problems	Easy	sql
2041	Accepted Candidates From the Interviews	Medium	sql
2051	The Category of Each Member in the Store	Medium	sql
2066	Account Balance	Medium	sql
2072	The Winner University	Easy	sql
2082	The Number of Rich Customers	Easy	sql
2084	Drop Type 1 Orders for Customers With Type 0 Orders	Medium	sql
2112	The Airport With the Most Traffic	Medium	sql
2118	Build the Equation	Hard	sql
2142	The Number of Passengers in Each Bus I	Medium	sql
2153	The Number of Passengers in Each Bus II	Hard	sql
2159	Order Two Columns Independently	Medium	sql
2173	Longest Winning Streak	Hard	sql
2175	The Change in Global Rankings	Medium	sql
2199	Finding the Topic of Each Post	Hard	sql
2205	The Number of Users That Are Eligible for Discount	Easy	sql
2228	Users With Two Purchases Within Seven Days	Medium	sql
2230	The Users That Are Eligible for Discount	Easy	sql
2238	Number of Times a Driver Was a Passenger	Medium	sql
2252	Dynamic Pivoting of a Table	Hard	sql
2253	Dynamic Unpivoting of a Table	Hard	sql
2292	Products With Three or More Orders in Two Consecutive Years	Medium	sql
2298	Tasks Count in the Weekend	Medium	sql
2308	Arrange Table by Gender	Medium	sql
2314	The First Day of the Maximum Recorded Degree in Each City	Medium	sql
2324	Product Sales Analysis IV	Medium	sql
2329	Product Sales Analysis V	Medium	sql
2339	All the Matches of the League	Easy	sql
2346	Compute the Rank as a Percentage	Medium	sql
2356	Number of Unique Subjects Taught by Each Teacher	Easy	sql
2362	Generate the Invoice	Hard	sql
2372	Calculate the Influence of Each Salesperson	Medium	sql
2377	Sort the Olympic Table	Easy	sql
2388	Change Null Values in a Table to the Previous Value	Medium	sql
2394	Employees With Deductions	Medium	sql
2474	Customers With Strictly Increasing Purchases	Hard	sql
2480	Form a Chemical Bond	Easy	sql
2494	Merge Overlapping Events in the Same Hall	Hard	sql
2504	Concatenate the Name and the Profession	Easy	sql
2668	Find Latest Salaries	Easy	sql
2669	Count Artist Occurrences On Spotify Ranking List	Easy	sql
2686	Immediate Food Delivery III	Medium	sql
2687	Bikes Last Time Used	Easy	sql
2688	Find Active Users	Medium	sql
2701	Consecutive Transactions with Increasing Amounts	Hard	sql
2720	Popularity Percentage	Hard	sql
2738	Count Occurrences in Text	Medium	sql
2752	Customers with Maximum Number of Transactions on Consecutive Days	Hard	sql
2783	Flight Occupancy and Waitlist Analysis	Medium	sql
2793	Status of Flight Tickets	Hard	sql
2820	Election Results	Medium	sql
2837	Total Traveled Distance	Easy	sql
2853	Highest Salaries Difference	Easy	sql
2854	Rolling Average Steps	Medium	sql
2877	Create a DataFrame from List	Easy	sql
2878	Get the Size of a DataFrame	Easy	sql
2879	Display the First Three Rows	Easy	sql
2880	Select Data	Easy	sql
2881	Create a New Column	Easy	sql
2882	Drop Duplicate Rows	Easy	sql
2883	Drop Missing Data	Easy	sql
2884	Modify Columns	Easy	sql
2885	Rename Columns	Easy	sql
2886	Change Data Type	Easy	sql
2887	Fill Missing Data	Easy	sql
2888	Reshape Data: Concatenate	Easy	sql
2889	Reshape Data: Pivot	Easy	sql
2890	Reshape Data: Melt	Easy	sql
2891	Method Chaining	Easy	sql
2893	Calculate Orders Within Each Interval	Medium	sql
2922	Market Analysis III	Medium	sql
2978	Symmetric Coordinates	Medium	sql
2984	Find Peak Calling Hours for Each City	Medium	sql
2985	Calculate Compressed Mean	Easy	sql
2986	Find Third Transaction	Medium	sql
2987	Find Expensive Cities	Easy	sql
2988	Manager of the Largest Department	Medium	sql
2989	Class Performance	Medium	sql
2990	Loan Types	Easy	sql
2991	Top Three Wineries	Hard	sql
2993	Friday Purchases I	Medium	sql
2994	Friday Purchases II	Hard	sql
2995	Viewers Turned Streamers	Hard	sql
3050	Pizza Toppings Cost Analysis	Medium	sql
3051	Find Candidates for Data Scientist Position	Easy	sql
3052	Maximize Items	Hard	sql
3053	Classifying Triangles by Lengths	Easy	sql
3054	Binary Tree Nodes	Medium	sql
3055	Top Percentile Fraud	Medium	sql
3056	Snaps Analysis	Medium	sql
3057	Employees Project Allocation	Hard	sql
3058	Friends With No Mutual Friends	Medium	sql
3059	Find All Unique Email Domains	Easy	sql
3060	User Activities within Time Bounds	Hard	sql
3061	Calculate Trapping Rain Water	Hard	sql
3087	Find Trending Hashtags	Medium	sql
3089	Find Bursty Behavior	Medium	sql
3103	Find Trending Hashtags II	Hard	sql
3118	Friday Purchase III	Medium	sql
3124	Find Longest Calls	Medium	sql
3126	Server Utilization Time	Medium	sql
3140	Consecutive Available Seats II	Medium	sql
3150	Invalid Tweets II	Easy	sql
3156	Employee Task Duration and Concurrent Tasks	Hard	sql
3166	Calculate Parking Fees and Duration	Medium	sql
3172	Second Day Verification	Easy	sql
3182	Find Top Scoring Students	Medium	sql
3188	Find Top Scoring Students II	Hard	sql
3198	Find Cities in Each State	Easy	sql
3204	Bitwise User Permissions Analysis	Medium	sql
3214	Year on Year Growth Rate	Hard	sql
3220	Odd and Even Transactions	Medium	sql
3230	Customer Purchasing Behavior Analysis	Medium	sql
3236	CEO Subordinate Hierarchy	Hard	sql
3246	Premier League Table Ranking	Easy	sql
3252	Premier League Table Ranking II	Medium	sql
3262	Find Overlapping Shifts	Medium	sql
3268	Find Overlapping Shifts II	Hard	sql
3278	Find Candidates for Data Scientist Position II	Medium	sql
3293	Calculate Product Final Price	Medium	sql
3308	Find Top Performing Driver	Medium	sql
3322	Premier League Table Ranking III	Medium	sql
3328	Find Cities in Each State II	Medium	sql
3338	Second Highest Salary II	Medium	sql
3358	Books with NULL Ratings	Easy	sql
3368	First Letter Capitalization	Hard	sql
3374	First Letter Capitalization II	Hard	sql
3384	Team Dominance by Pass Success	Hard	sql
3390	Longest Team Pass Streak	Hard	sql
3401	Find Circular Gift Exchange Chains	Hard	sql
3415	Find Products with Three Consecutive Digits	Easy	sql
3421	Find Students Who Improved	Medium	sql
3436	Find Valid Emails	Easy	sql
3451	Find Invalid IP Addresses	Hard	sql
3465	Find Products with Valid Serial Numbers	Easy	sql
3475	DNA Pattern Recognition	Medium	sql
3482	Analyze Organization Hierarchy	Hard	sql
3497	Analyze Subscription Conversion	Medium	sql
3521	Find Product Recommendation Pairs	Medium	sql
3554	Find Category Recommendation Pairs	Hard	sql
3564	Seasonal Sales Analysis	Medium	sql
3570	Find Books with No Available Copies	Easy	sql
3580	Find Consistently Improving Employees	Medium	sql
3586	Find COVID Recovery Patients	Medium	sql
3601	Find Drivers with Improved Fuel Efficiency	Medium	sql
3611	Find Overbooked Employees	Medium	sql
3617	Find Students with Study Spiral Pattern	Hard	sql
3626	Find Stores with Inventory Imbalance	Medium	sql
3642	Find Books with Polarized Opinions	Easy	sql
3657	Find Loyal Customers	Medium	sql
3673	Find Zombie Sessions	Hard	sql
3705	Find Golden Hour Customers	Medium	sql
3716	Find Churn Risk Customers	Medium	sql
3764	Most Common Course Pairs	Hard	sql
3793	Find Users with High Token Usage	Easy	sql
3808	Find Emotionally Consistent Users	Medium	sql
3832	Find Users with Persistent Behavior Patterns	Hard	sql