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SQL Arena

SQL Problems Catalog from Top Companies

Over-the-Counter Medications
Customers from Berlin
Platinum-Tier Members
Long-Haul Flights
Berlin Clubs
Premium Subscriptions
5-Star Hotels
Spacious Rooms
Rock Artists
Festivals in 2024
Endangered Species
Savanna Residents
Clients with non-expired applications
Medications above 6 euros
Product Showcase: Rename the Columns
Customer card: projection with aliases
Products from two warehouses
Catalog Without Archive
Products Under 1000 Rubles
Delivered Orders
Warehouse shelf: SKU, weight and price under readable names
Drop Unrated Reviews, Replace Empty Comments
Kotomarket showcase: three categories with IN
Unique category-supplier pairs
Kotomarket showcase: price tiers and the top 5
Unique Category–Supplier Pairs in the Mid Price Range
Kotomarket: status labels for orders of customers starting with "А"
Paid Events Across Cities
Which Platform Converts Best
What Cities View and Buy
Large Order or Regular
Numeric Codes Without Failures
Platforms That Saw a Payment
A Leaner Event Log
Purchases Without Internal Details
Sessions Without Purchase Counts
One Row per Item
Items in Each Basket
A Basket in the Log
Platforms for the New Report
Inside Each Event Session
Sessions That Ran Long
Three Days in One Read
Weekdays in the Event Log
When Kotomarket Comes Alive
A Preview Without the Heavy Columns
The Three Largest Receipts
Unrecognized Name
Readings Through the Garbage
Faults in the Sensor Log
The Two Clocks at the Door
The City Inside the JSON
A day of faults: reading the whole log
User activity: views and purchases
Views and purchases per product
Events per day (ClickHouse)
Events per hour bucket (ClickHouse)
Event distribution by hour of day (ClickHouse)
Each user's set of products
Distinct products per user
Total revenue per user
Order count per user
Most expensive purchased product per user
Cheapest purchased product per user
Purchase sequence number per user
Median session duration by country
Median and average duration by device
Sessions per device
Bounce rate per device
Bounced vs engaged sessions per device
Distinct pages per user
Distinct countries per device
Number of distinct pages per user
Row counts by status code (ClickHouse)
Average latency per service
Min and max latency per service
Latency stats per log level
Success rate by payment method (ClickHouse)
Successful revenue by method (ClickHouse)
Overall payment-success summary (ClickHouse)
Tickets containing кот
Cities without москва
Tickets with kotomarket.ru domain
Phones containing +7
Names containing the letter ё
Lines with 5xx HTTP status
Phones before a parenthesis
Tickets containing a time
Remove fragments in HTML tags
Phones with 11 digits
Tickets containing the word кот
Valid email addresses
Logs with error statuses
First order code
Dates in ISO format
Repeated word in tickets
Mask a card number
Count order codes
Server errors in nginx
Domains of splittable email addresses
Promo codes after the label
All orders of one buyer
How many orders each buyer has
A foreign key with no index
Discount on Action games
The feed of latest orders
Payments for an order
The latest payments
One customer's orders through the link
All the payments of an order
Where this product was sold
Pages with no likes
Parts with unfinished assembly
Laptop and mobile views
Top 3 cities by completed trades
Duplicate job listings
Most active message senders in August 2022
Average product rating by month
Difference between highest and lowest card issuance
Average items per order from compressed data
Drug sales by manufacturer
Spare datacenter capacity
Final balance by account
Apple Pay and other payment totals
Sign-up confirmed the next day
Employees earning more than their manager
Full fan roster
Names ending with `man`
Number of club concerts
Venue types for Moscow concerts
Departures from Paris
Bands departing from Vladivostok
Longest fan name
Fan count per concert
The club's oldest member
Number of cardiology wards
Patients with Maple Ave in their address
Female patients named Mary
Patient count in ward CARD-B
Start time of the 4th slot
Duration from slot 2 to slot 4
Wards where Bennett holds appointments
Bennett's appointments on August 30, 2019
Ward occupancy
Delete departures from Moscow
Passengers with .by email addresses
Doctors in neurology wards
Patients in alphabetical order
Cabins with the full amenity package
Tour leg timetable
Wi-Fi availability by cabin
Patients born in May
Passengers with Hotmail email addresses
Facebook Pages That Got No Likes
Unfinished Parts: Alternate Version
Messages Sent per User
Combined Client Balance
Real Estate in Moscow
Cities Hosting Properties
Second-Best Pilot by Passengers
Mean Driver Score
High-Scoring Game Sessions
Actor-Director Duos with 3+ Films
Joining Two Tables
Customers Who Never Ordered
Repeated Email Entries
Crew Size per Worker
Distinct Friend Requests
Gaming Analytics 1: Initial Login
Gaming Analytics 2: Device Choice
Share of Same-Day Deliveries
Comments Under Posts
Sales Volume by Product
Flagged Posts
Swap Salary
Create Projects Table
Add a test user
Drop the Departments Table
Seed a batch of test orders
Add Email Column
Purge stale audit log rows
Drop Salary Column
Rename Column name
Index on Employee Name
Active Employees View
Customers who already ordered something
Customers who never placed an order
Find orders bigger than average
Products that ever sold
Products that nobody bought
Find the most expensive item
Customers from your top-buying country
Pull orders from Russian customers only
Cheapest pick in every category
Show every customer's order count
Save your first journal entry
Pin one note so it stays at the top
Pin every January note for the new year
Delete one note that's no longer needed
Spring cleaning — drop everything unpinned
Scaffold the users table for a new SaaS
Add a phone field — product asked
Drop a column nobody uses anymore
Link a book to its author — no orphans
Speed up the logs dashboard
Staff Bonuses
Finding Who Referred Each Customer
Authors Who Read Themselves
Subscriber Tally
Classes Having 5+ Pupils
Flipping Employee Genders
Actor & Director Pairs (3+ Movies)
High-Balance Bank Clients
Leads and Partners per Day
Aggregate Staff Working Hours
Computing the Special Bonus
Most Recent 2020 Login
Checking Email Validity
Products with Proper Serials
Books Out of Stock
Students Studying 3+ Subjects
Stale Session Leftovers
Negative Stock Balances
Statuses as One List
Idempotency Key Store
Default App Theme
Guest Orders
Guest-Safe Order Label
Guests at the End
All Statuses Without Repeats
Guest Orders as 0
Bulk-cancel pending orders
Delete cancelled orders
Raise kitchen prices by 10%
Restock the office category
Log with an auto identifier
Tickets with a restricted status
Employees in FIO format
Client spend in the last 30 days
Daily views and unique audience
Average age of Smartwatch buyers in 2024
Country where the city Salzburg is located
Population by region
Active warehouses per city
Buyers of a SKU on a given date
Price category without CASE or IF (Yandex Praktikum)
Revenue from female audience
Works published more than 5 times
Courses with average rating (10+ ratings only)
OTP category with the most code entries
Daily product turnover at the bank
Active SCD2 record version on a given date
Row count for DISTINCT over a GROUP BY aggregate
Revenue by course in the last month
Active users on a given date
OTP-category indicator flag
Average family-income gap: even vs odd-id borrowers
Gaps between plays
Session-start flag in an online store
Orders out of a JSON payload
Hotel guests from nested JSON
A menu without shouting or whispering
The spaces that break routing
The patient name on the wristband
Monthly Sales Pulse
Listening Hours by Month
Parcel scans after the watermark
Store delivery scorecard
Second-level shelves
Comparable apartment pairs
Documentary watchers
Which Customers Need a Win-Back Campaign?
Purchase Frequency in an Audio App
The Lab: Tests Still Without Results
Telecom: Subscriber Display Name
Wine Bar: Bookings Without Confirmation
One register for every delivery leg
What was watched, without repeats
One-to-one, one-to-many
Row fan-out after a JOIN
Duplicate Parcel Registrations
Incomplete Streaming Catalog Records
Neobank Operating Balance
From KYC Submission to Approval
A Customer's First Digital Footprint
Streaming Cohorts on the Calendar

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