Problems
Every problem is checked on a real database. Solved ones earn XP and count toward your group’s ranking.
ProblemTopicDatabaseLevelXP
- List of departmentsSELECT · IT companySELECTIT companyEasy20
- Well paidWHERE · IT companyWHEREIT companyEasy20
- Departments in TashkentWHERE · IT companyWHEREIT companyEasy20
- Hired in 2025Sana · IT companySanaIT companyEasy20
- No departmentNULL · IT companyNULLIT companyEasy20
- Top five salariesORDER BY · IT companyORDER BYIT companyEasy20
- Running projectsNULL · IT companyNULLIT companyEasy20
- Job titlesDISTINCT · IT companyDISTINCTIT companyEasy20
- Names starting with SLIKE · IT companyLIKEIT companyEasy20
- Mid-range salariesBETWEEN · IT companyBETWEENIT companyEasy20
- BookshelfORDER BY · Online storeORDER BYOnline storeEasy20
- Apple productsWHERE · Online storeWHEREOnline storeEasy20
- Running lowBETWEEN · Online storeBETWEENOnline storeEasy20
- Paid in cashAND · Online storeANDOnline storeEasy20
- Customers of 2026Sana · Online storeSanaOnline storeEasy20
- Gmail usersLIKE · Online storeLIKEOnline storeEasy20
- Unhappy reviewsIN · Online storeINOnline storeEasy20
- Ten percent offIfoda · Online storeIfodaOnline storeEasy20
- Long ridesWHERE · Taxi serviceWHERETaxi serviceEasy20
- White carsWHERE · Taxi serviceWHERETaxi serviceEasy20
- Drivers of 2026Sana · Taxi serviceSanaTaxi serviceEasy20
- Within one districtUstunlarni solishtirish · Taxi serviceUstunlarni solishtirishTaxi serviceEasy20
- Generous tipsWHERE · Taxi serviceWHERETaxi serviceEasy20
- First-year girlsWHERE · UniversityWHEREUniversityEasy20
- Grant holders from TashkentAND · UniversityANDUniversityEasy20
- ProfessorsWHERE · UniversityWHEREUniversityEasy20
- First-semester subjectsORDER BY · UniversityORDER BYUniversityEasy20
- Russian-language groupsWHERE · UniversityWHEREUniversityEasy20
- Near-perfect scoresWHERE · UniversityWHEREUniversityEasy20
- Youngest studentsLIMIT · UniversityLIMITUniversityEasy20
- Headcount by departmentGROUP BY · IT companyGROUP BYIT companyMedium40
- Average pay by departmentAVG · IT companyAVGIT companyMedium40
- Who works whereJOIN · IT companyJOINIT companyMedium40
- Monthly payrollSUM · IT companySUMIT companyMedium40
- Big departmentsHAVING · IT companyHAVINGIT companyMedium40
- Hours per projectSUM · IT companySUMIT companyMedium40
- Oldest and youngestMIN / MAX · IT companyMIN / MAXIT companyMedium40
- Hires per yearEXTRACT · IT companyEXTRACTIT companyMedium40
- Popular positionsHAVING · IT companyHAVINGIT companyMedium40
- Employee and managerSelf JOIN · IT companySelf JOINIT companyMedium40
- Delivered revenueJOIN + SUM · Online storeJOIN + SUMOnline storeMedium40
- Most active buyersGROUP BY · Online storeGROUP BYOnline storeMedium40
- Rating by categoryJOIN + AVG · Online storeJOIN + AVGOnline storeMedium40
- How many brandsCOUNT DISTINCT · Online storeCOUNT DISTINCTOnline storeMedium40
- Price range by categoryMIN / MAX · Online storeMIN / MAXOnline storeMedium40
- Lines per orderHisob-kitob · Online storeHisob-kitobOnline storeMedium40
- Cancellations by cityHAVING · Online storeHAVINGOnline storeMedium40
- Reviewed productsCOUNT DISTINCT · Online storeCOUNT DISTINCTOnline storeMedium40
- Busy driversHAVING · Taxi serviceHAVINGTaxi serviceMedium40
- Average fare by tariffJOIN + AVG · Taxi serviceJOIN + AVGTaxi serviceMedium40
- Money by payment methodSUM · Taxi serviceSUMTaxi serviceMedium40
- Trip outcomesGROUP BY · Taxi serviceGROUP BYTaxi serviceMedium40
- Fleet by yearGROUP BY · Taxi serviceGROUP BYTaxi serviceMedium40
- Where trips endGROUP BY · Taxi serviceGROUP BYTaxi serviceMedium40
- Group sizesGROUP BY · UniversityGROUP BYUniversityMedium40
- Average score per subjectAVG · UniversityAVGUniversityMedium40
- Failed examsCOUNT · UniversityCOUNTUniversityMedium40
- Languages of studyGROUP BY · UniversityGROUP BYUniversityMedium40
- Scholarship budgetSUM · UniversitySUMUniversityMedium40
- Final-year students and facultiesJOIN · UniversityJOINUniversityMedium40
- Second-highest salaryIchki so‘rov · IT companyIchki so‘rovIT companyHard80
- Above the department averageBog‘langan ichki so‘rov · IT companyBog‘langan ichki so‘rovIT companyHard80
- Earns more than the managerSelf JOIN · IT companySelf JOINIT companyHard80
- Top earner per departmentOyna funksiyasi · IT companyOyna funksiyasiIT companyHard80
- Empty departmentsLEFT JOIN · IT companyLEFT JOINIT companyHard80
- Employees without projectsNOT EXISTS · IT companyNOT EXISTSIT companyHard80
- MultitaskersHAVING · IT companyHAVINGIT companyHard80
- Direct reportsSelf JOIN + GROUP BY · IT companySelf JOIN + GROUP BYIT companyHard80
- Salary ladderDENSE_RANK · IT companyDENSE_RANKIT companyHard80
- Growing teamO‘sib boruvchi yig‘indi · IT companyO‘sib boruvchi yig‘indiIT companyHard80
- Budget per hourJOIN + ifoda · IT companyJOIN + ifodaIT companyHard80
- The whole teamRekursiv CTE · IT companyRekursiv CTEIT companyHard80
- Helping other departmentsBir nechta JOIN · IT companyBir nechta JOINIT companyHard80
- Share of the payrollOyna funksiyasi · IT companyOyna funksiyasiIT companyHard80
- Department veteransBog‘langan ichki so‘rov · IT companyBog‘langan ichki so‘rovIT companyHard80
- Category bestsellersOyna funksiyasi · Online storeOyna funksiyasiOnline storeHard80
- Returning customersCTE + CASE · Online storeCTE + CASEOnline storeHard80
- Month over monthLAG · Online storeLAGOnline storeHard80
- Silent buyersNOT EXISTS · Online storeNOT EXISTSOnline storeHard80
- Sold at a discountJOIN + ifoda · Online storeJOIN + ifodaOnline storeHard80
- Delivery speedSana farqi · Online storeSana farqiOnline storeHard80
- Driver leaderboardRANK · Taxi serviceRANKTaxi serviceHard80
- Busiest dayCTE · Taxi serviceCTETaxi serviceHard80
- Loyal ridersHAVING · Taxi serviceHAVINGTaxi serviceHard80
- Average speedVaqt farqi · Taxi serviceVaqt farqiTaxi serviceHard80
- Never failedHAVING · UniversityHAVINGUniversityHard80
- Faculty rankingRANK · UniversityRANKUniversityHard80
- Five-point scaleCASE · UniversityCASEUniversityHard80
- Strict teachersJOIN + HAVING · UniversityJOIN + HAVINGUniversityHard80
- Bigger-than-average groupsIchki so‘rov HAVING ichida · UniversityIchki so‘rov HAVING ichidaUniversityHard80