SQL problems
Write a query against real tables. Run checks it on sample data; Submit also checks hidden databases with edge cases like NULLs and ties.
Easy 15Medium 20Hard 10
- Account Balance TiersCase When · Null Handlingeasy
- Average Score per SubjectAggregation · Null Handling · Sortingeasy
- Campaign Click-Through RateSelect Filter · Null Handlingeasy
- Customer Email DomainsStrings · Group By · Sortingeasy
- Customers Who Never OrderedJoins · Null Handlingeasy
- Department HeadcountJoins · Aggregation · Sortingeasy
- Duplicate Signup EmailsGroup By · Having · Stringseasy
- Employees Without a ManagerSelect Filter · Null Handlingeasy
- High-Value Delivered OrdersSelect Filter · Sortingeasy
- Late ShipmentsDates · Select Filter · Sortingeasy
- Monthly Signup CountsDates · Group Byeasy
- Open Tickets by PriorityAggregation · Group Byeasy
- Total Successful PaymentsAggregation · Group By · Sortingeasy
- User Display NamesNull Handling · Strings · Case Wheneasy
- Wishlist Items Also in CartSet Operationseasy
- Campaign Click-to-ConversionJoins · Subqueries · Ctesmedium
- Class Rank by Total ScoreRanking · Null Handling · Group Bymedium
- Cumulative Hires by YearRunning Totals · Dates · Group Bymedium
- Daily Active Users with a 3-Day AverageWindow Functions · Dates · Aggregationmedium
- Deduplicate Marketing LeadsDeduplication · Window Functions · Stringsmedium
- Employees Who Out-Earn Their ManagerSelf Joinmedium
- Latest Status per ShipmentWindow Functions · Deduplicationmedium
- Ledger Running BalanceRunning Totals · Window Functionsmedium
- Loans by Missed InstallmentsJoins · Case When · Aggregationmedium
- Month-over-Month RevenueWindow Functions · Dates · Aggregationmedium
- Orders by Day of WeekDates · Case When · Group Bymedium
- Products Sold but Never ReturnedSet Operations · Null Handling · Subqueriesmedium
- Quarterly Sales PivotPivot · Case When · Datesmedium
- Repeat Buyers Within 30 DaysWindow Functions · Datesmedium
- Salary Share of DepartmentWindow Functions · Aggregationmedium
- Second-Highest Salary per DepartmentRanking · Window Functionsmedium
- Students Above Their Class AverageSubqueries · Null Handlingmedium
- Subscription Churn by PlanAggregation · Case When · Null Handlingmedium
- Ticket First Response TimeJoins · Dates · Null Handlingmedium
- Top Two Products per CategoryTop N Per Group · Window Functions · Joinsmedium
- Bill of Materials ExplosionRecursive Cte · Aggregationhard
- Customers Driving 80% of RevenueRunning Totals · Window Functions · Cteshard
- Daily Revenue with Missing Days FilledRecursive Cte · Dates · Running Totalshard
- Longest Login StreakGaps And Islands · Window Functions · Dateshard
- Median Delivery Days per CarrierWindow Functions · Dates · Aggregationhard
- Next-Month Retention by Signup CohortCtes · Dates · Subquerieshard
- Org Chart Reporting ChainRecursive Cte · Stringshard
- Overlapping Driver DeliveriesSelf Join · Dateshard
- Price Effective at Order TimeSubqueries · Dates · Joinshard
- Sessionize App EventsGaps And Islands · Window Functions · Dateshard