| 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 With at Least 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 Sex of Employees | 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 | Database | Medium | 🔒 |
| 3089 | Find Bursty Behavior | Database | Medium | 🔒 |
| 3103 | Find Trending Hashtags II | Database | Hard | 🔒 |
| 3118 | Friday Purchase III | Database | Medium | 🔒 |
| 3124 | Find Longest Calls | Database | Medium | 🔒 |
| 3126 | Server Utilization Time | Database | Medium | 🔒 |
| 3140 | Consecutive Available Seats II | Database | Medium | 🔒 |
| 3150 | Invalid Tweets II | Database | Easy | 🔒 |
| 3156 | Employee Task Duration and Concurrent Tasks | Database | Hard | 🔒 |
| 3166 | Calculate Parking Fees and Duration | Database | Medium | 🔒 |
| 3172 | Second Day Verification | Database | Easy | 🔒 |
| 3182 | Find Top Scoring Students | Database | Medium | 🔒 |
| 3188 | Find Top Scoring Students II | Database | Hard | 🔒 |
| 3198 | Find Cities in Each State | Database | Easy | 🔒 |
| 3204 | Bitwise User Permissions Analysis | Database | Medium | 🔒 |
| 3214 | Year on Year Growth Rate | Database | Hard | 🔒 |
| 3220 | Odd and Even Transactions | Database | Medium | |
| 3230 | Customer Purchasing Behavior Analysis | Database | Medium | 🔒 |
| 3236 | CEO Subordinate Hierarchy | Database | Hard | 🔒 |
| 3246 | Premier League Table Ranking | Database | Easy | 🔒 |
| 3252 | Premier League Table Ranking II | Database | Medium | 🔒 |
| 3262 | Find Overlapping Shifts | Database | Medium | 🔒 |
| 3268 | Find Overlapping Shifts II | Database | Hard | 🔒 |
| 3278 | Find Candidates for Data Scientist Position II | Database | Medium | 🔒 |
| 3293 | Calculate Product Final Price | Database | Medium | 🔒 |
| 3308 | Find Top Performing Driver | Database | Medium | 🔒 |
| 3322 | Premier League Table Ranking III | Database | Medium | 🔒 |
| 3328 | Find Cities in Each State II | Database | Medium | 🔒 |
| 3338 | Second Highest Salary II | Database | Medium | 🔒 |
| 3358 | Books with NULL Ratings | Database | Easy | 🔒 |
| 3368 | First Letter Capitalization | Database | Hard | 🔒 |
| 3374 | First Letter Capitalization II | Database | Hard | |
| 3384 | Team Dominance by Pass Success | Database | Hard | 🔒 |
| 3390 | Longest Team Pass Streak | Database | Hard | 🔒 |
| 3401 | Find Circular Gift Exchange Chains | Database | Hard | 🔒 |
| 3415 | Find Products with Three Consecutive Digits | Database | Easy | 🔒 |
| 3421 | Find Students Who Improved | Database | Medium | |
| 3436 | Find Valid Emails | Database | Easy | |
| 3451 | Find Invalid IP Addresses | Database | Hard | |
| 3465 | Find Products with Valid Serial Numbers | Database | Easy | |
| 3475 | DNA Pattern Recognition | | Medium | |
| 3482 | Analyze Organization Hierarchy | Database | Hard | |
| 3497 | Analyze Subscription Conversion | Database | Medium | |
| 3521 | Find Product Recommendation Pairs | Database | Medium | |
| 3554 | Find Category Recommendation Pairs | Database | Hard | |
| 3564 | Seasonal Sales Analysis | Database | Medium | |
| 3570 | Find Books with No Available Copies | Database | Easy | |
| 3580 | Find Consistently Improving Employees | Database | Medium | |
| 3586 | Find COVID Recovery Patients | Database | Medium | |
| 3601 | Find Drivers with Improved Fuel Efficiency | Database | Medium | |
| 3611 | Find Overbooked Employees | Database | Medium | |
| 3617 | Find Students with Study Spiral Pattern | | Hard | |
| 3626 | Find Stores with Inventory Imbalance | | Medium | |
| 3642 | Find Books with Polarized Opinions | | Medium | |
| 3657 | Find Loyal Customers | | Medium | |
| 3673 | Find Zombie Sessions | | Hard | |
| 3705 | Find Golden Hour Customers | | Medium | |
| 3716 | Find Churn Risk Customers | | Medium | |
| 3764 | Most Common Course Pairs | | Hard | |
| 3793 | Find Users with High Token Usage | | Easy | |
| 3808 | Find Emotionally Consistent Users | | Medium | |
| 3832 | Find Users with Persistent Behavior Patterns | | Hard | |
