SQL practice problems

Customers Without Orders

E-commerce — Customers, Orders & Items · ~15 min

Return the names of customers who have never placed an order.

E-commerce — Customers, Orders & Items

~15 min

Active Accounts per Customer

Banking — Card Transactions · ~15 min

The customer relations manager needs a list of all customers who currently have active accounts, to coordinate engagement efforts. Return full name (the…

Banking — Card Transactions

~15 min

Customer Email and Account Number List

Banking — Card Transactions · ~15 min

The customer support team wants to quickly look up customer details when handling account inquiries. They need a list of every customer who has at least one…

Banking — Card Transactions

~15 min

List Cardholders and Their Card Networks

Banking — Card Transactions · ~15 min

The marketing team wants to understand which card networks are used by each customer for targeted promotions. For every customer who holds a card, provide…

Banking — Card Transactions

~15 min

Customer Emails with Active Accounts

Banking — Card Transactions · ~15 min

The customer engagement team needs a contact list for customers who presently hold active accounts, to inform them of important updates. Return email: the…

Banking — Card Transactions

~15 min

Employee Department List

HR — Departments & Employees · ~15 min

The HR department is updating the company directory and needs to verify which employees are assigned to which departments. They require a list showing every…

HR — Departments & Employees

~15 min

Employee Department List

HR — Departments & Employees · ~15 min

The HR director needs a current roster showing which department each employee is assigned to, to ensure all departmental records are accurate and up to date.…

HR — Departments & Employees

~15 min

List Employee Names and Departments

HR — Departments & Employees · ~15 min

A company HR analyst needs a clear overview of all employees and the departments they are currently assigned to, in order to verify department memberships and…

HR — Departments & Employees

~15 min

Headcount per Department

HR — Departments & Employees · ~15 min

Return each department name and the number of employees in it. Departments with no employees should appear with a count of 0.

HR — Departments & Employees

~15 min

7-Day Rolling Revenue and Signups

Analytics — Daily Metrics · ~25 min

The analytics team wants to analyze trends by creating a 7 day rolling summary of both revenue and signups for each day in the dataset. They need to see, for…

Analytics — Daily Metrics

~25 min

Top Transaction per Customer by Amount

Banking — Card Transactions · ~25 min

The fraud monitoring team wants to review the largest transaction for each customer, along with the merchant and card details, to spot any unusual activity.…

Banking — Card Transactions

~25 min

Top Customer per Country by Total Spend

E-commerce — Customers, Orders & Items · ~25 min

The international sales team wants to recognize the top spending customer in each country for their cumulative purchases. For each order, they want to see the…

E-commerce — Customers, Orders & Items

~25 min

Revenue and Signups by Day with Minimum Sales

Analytics — Daily Metrics · ~25 min

The analytics team is reviewing how daily sales performance aligns with new user signups. They want to analyze only days with strong sales to understand user…

Analytics — Daily Metrics

~25 min

Top Selling Product Categories by Country

E-commerce — Customers, Orders & Items · ~25 min

The international sales team wants to identify which product categories are most popular in each country to inform regional marketing campaigns. For each…

E-commerce — Customers, Orders & Items

~25 min

Average Salary by Department with Minimum Headcount

HR — Departments & Employees · ~25 min

The HR team wants to identify which departments have a sufficient number of employees and to analyze their average salaries. They need a report listing each…

HR — Departments & Employees

~25 min

Average Salary per Department with Minimum Employee Count

HR — Departments & Employees · ~25 min

The HR team is assessing department sizes and their average salaries to identify well staffed teams. They want to see the average salary for each department…

HR — Departments & Employees

~25 min

Top-Selling Product Categories by Country

E-commerce — Customers, Orders & Items · ~25 min

The international sales team wants to understand which product categories are most popular in each country to tailor regional promotions. For each country that…

E-commerce — Customers, Orders & Items

~25 min

Average Salary by Department for Departments with Multiple Employees

HR — Departments & Employees · ~25 min

The HR analytics team wants to understand salary trends across different departments, but only for departments that have more than one employee. This will help…

HR — Departments & Employees

~25 min

Top Spending Customers by Country

Banking — Card Transactions · ~25 min

The finance team wants to identify the top 3 customers by total transaction spending in each country. This will help them understand their most valuable…

Banking — Card Transactions

~25 min

Signup Conversion Rate by Region

Analytics — Daily Metrics · ~25 min

The marketing team wants to understand which regions are most effective at converting new signups into paying customers. For each region that had at least 5…

Analytics — Daily Metrics

~25 min

Monthly Transaction Volume by Account Type

Banking — Card Transactions · ~25 min

The finance team wants to understand how transaction activity varies by account type and month to identify trends in customer usage. They need a report that…

Banking — Card Transactions

~25 min

Average Salary by Department (With Minimum Employee Count)

HR — Departments & Employees · ~25 min

The HR team wants to review average salaries across departments but only for departments with at least 3 employees. They need this information to identify…

HR — Departments & Employees

~25 min

Total Spend per Customer by Country

Banking — Card Transactions · ~25 min

The marketing team is analyzing customer spending patterns to identify top customers in different countries. They want to see the total transaction amount for…

Banking — Card Transactions

~25 min

Average Salary by Department with Minimum Headcount

HR — Departments & Employees · ~25 min

The HR analytics team wants to identify departments with enough staff to analyze compensation trends. They are interested in departments that have at least 3…

HR — Departments & Employees

~25 min

Average Salary by Department with Minimum Staff

HR — Departments & Employees · ~25 min

The HR team is analyzing compensation trends across the company and wants to focus on departments with a substantial number of employees. They need to know the…

HR — Departments & Employees

~25 min

Top Merchants by Transaction Count per Country

Banking — Card Transactions · ~25 min

The international business team wants to identify which merchants are most active in each country to support partnership negotiations. For every country where…

Banking — Card Transactions

~25 min

Department Average Salary and Headcount

HR — Departments & Employees · ~25 min

The HR analytics team is preparing a report on department staffing and pay. They want to see the average salary and total number of employees for each…

HR — Departments & Employees

~25 min

Regional Signup-to-Order Ratio by Day

Analytics — Daily Metrics · ~25 min

The marketing analytics team wants to understand how the ratio of new user signups to orders varies by region and day. They want to focus on days and regions…

Analytics — Daily Metrics

~25 min

Average Salary per Department with Minimum Staff

HR — Departments & Employees · ~25 min

The HR team is reviewing compensation across the company and wants to focus on departments with a substantial number of employees. They need to see the average…

HR — Departments & Employees

~25 min

Average Salary by Department with Minimum Headcount

HR — Departments & Employees · ~25 min

The HR analytics team is reviewing compensation patterns across departments to identify areas with sufficient staffing and competitive pay. They want to see…

HR — Departments & Employees

~25 min

Total Spending per Customer by Country

Banking — Card Transactions · ~25 min

A regional sales manager wants to identify high value customers for a potential loyalty program. They need to know which customers have spent more than 1000 in…

Banking — Card Transactions

~25 min

Total Spending Per Customer in Home Country

Banking — Card Transactions · ~25 min

The finance analytics team wants to understand domestic spending patterns among customers. They need to see, for every customer who has spent money in their…

Banking — Card Transactions

~25 min

Total Spend Per Customer by Country

Banking — Card Transactions · ~25 min

The finance analytics team needs to identify high value customers for targeted international campaigns. For each customer, provide their name, home country,…

Banking — Card Transactions

~25 min

Average Order Value on High Signup Days

Analytics — Daily Metrics · ~25 min

A marketing analyst needs to evaluate sales outcomes on days with strong user acquisition to assess the impact of high signups on revenue. For every day where…

Analytics — Daily Metrics

~25 min

Weekly Sales and Signup Summary by Region

Analytics — Daily Metrics · ~25 min

The regional sales manager needs a weekly summary to track both sales performance and new customer signups across all regions. This report will help identify…

Analytics — Daily Metrics

~25 min

Running Total Revenue and Signups by Day

Analytics — Daily Metrics · ~25 min

Regional sales managers want to track daily performance alongside user growth to better understand how signups and revenue progress together. They need a…

Analytics — Daily Metrics

~25 min

Average Revenue Per Order by Day with High Signups

Analytics — Daily Metrics · ~25 min

The marketing team wants to evaluate how efficiently revenue is generated on days with high customer signups. For each day when at least 100 new users signed…

Analytics — Daily Metrics

~25 min

Average Revenue per Order for High Signup Days

Analytics — Daily Metrics · ~25 min

The marketing team wants to evaluate how sales performance correlates with high customer acquisition days. They are interested in each day where at least 100…

Analytics — Daily Metrics

~25 min

Top Customers by Total Spend

E-commerce — Customers, Orders & Items · ~25 min

The marketing department is planning a loyalty initiative and needs to focus on customers who have demonstrated frequent purchasing behavior. For each customer…

E-commerce — Customers, Orders & Items

~25 min

Top Customers by Total Spend

E-commerce — Customers, Orders & Items · ~25 min

The finance team is preparing a report on high value repeat customers to inform loyalty program decisions. They need a list showing each customer's name,…

E-commerce — Customers, Orders & Items

~25 min

Top Customers by Order Count

E-commerce — Customers, Orders & Items · ~25 min

The customer relations manager wants to recognize highly active customers for a new loyalty initiative. Provide a list of all customers who have placed more…

E-commerce — Customers, Orders & Items

~25 min

Top-Spending Customers by Country

E-commerce — Customers, Orders & Items · ~25 min

The marketing department is planning a rewards initiative and needs to know which customers have spent the most in each country. They want to see, for every…

E-commerce — Customers, Orders & Items

~25 min

Average Salary by Manager for Each Department

HR — Departments & Employees · ~25 min

Department heads want to recognize managers who oversee larger teams and understand compensation patterns within their departments. For each department,…

HR — Departments & Employees

~25 min

Average Salary by Department for Departments with At Least 3 Employees

HR — Departments & Employees · ~25 min

A compensation analyst is evaluating departments with a significant number of employees to benchmark salary levels. They need to identify all departments that…

HR — Departments & Employees

~25 min

Average Revenue per Signup by Day

Analytics — Daily Metrics · ~25 min

The marketing team needs a daily summary to assess how sales relate to new customer signups. For each day with at least one signup, provide the total revenue…

Analytics — Daily Metrics

~25 min

Revenue Performance by Region Category

Analytics — Daily Metrics · ~25 min

Regional managers want to quickly assess how each region is performing in terms of daily sales to prioritize support and recognize top performers. They need a…

Analytics — Daily Metrics

~25 min

Department Headcount Including Subordinates

HR — Departments & Employees · ~25 min

The HR analytics team is preparing a report to identify managers with significant team sizes across departments for organizational planning. They want to know…

HR — Departments & Employees

~25 min

Sales and Signup Conversion Rate by Day

Analytics — Daily Metrics · ~25 min

The marketing team needs a summary of how daily website signups translate into sales performance, focusing on days with significant user activity. They want to…

Analytics — Daily Metrics

~25 min

Cumulative Revenue and Signups by Day and Region

Analytics — Daily Metrics · ~25 min

Regional sales managers want to analyze both revenue and user acquisition trends over time. For each date and region, they need to see the daily revenue, the…

Analytics — Daily Metrics

~25 min

Employees With Above-Average Department Salary

HR — Departments & Employees · ~25 min

A department head wants to recognize employees who earn above average salaries compared to others in their department, in order to highlight high performers…

HR — Departments & Employees

~25 min

Top Earners Per Department

HR — Departments & Employees · ~25 min

The HR analytics team wants to recognize top earners within each department for a company wide report. They need a list showing every department alongside the…

HR — Departments & Employees

~25 min

Revenue per Customer (Completed Orders)

E-commerce — Customers, Orders & Items · ~25 min

For each customer that has at least one completed order, return the customer name and their total revenue (sum of quantity × unit price across completed…

E-commerce — Customers, Orders & Items

~25 min

Departments With More Than Two Employees

HR — Departments & Employees · ~25 min

Return the names of departments that have more than two employees.

HR — Departments & Employees

~25 min

Department Managers with Above-Average Salaries

HR — Departments & Employees · ~40 min

HR is preparing a report to identify managers whose salaries are above the average salary of their respective departments. For each such manager, list their…

HR — Departments & Employees

~40 min

Top Merchant Per Customer by Transaction Value

Banking — Card Transactions · ~40 min

The marketing analytics team wants to identify each customer's favorite merchant based on total transaction value for targeted partnership offers. For every…

Banking — Card Transactions

~40 min

Find the Missing Days (Gaps & Islands)

Analytics — Daily Metrics · ~40 min

The 'IN' region's daily data has a gap — some consecutive dates are missing entirely. Return the day where the data resumes after the gap, along with how many…

Analytics — Daily Metrics

~40 min

Day-over-Day Revenue Change

Analytics — Daily Metrics · ~40 min

For the 'US' region, return each day's revenue and its change from the previous day's revenue (delta = today − yesterday). The very first day in the series has…

Analytics — Daily Metrics

~40 min

7-Day Moving Average

Analytics — Daily Metrics · ~40 min

For the 'US' region only, return each day's revenue and a 7 day moving average (the current day plus the 6 days immediately before it), rounded to 2 decimal…

Analytics — Daily Metrics

~40 min

True Running Total With Salary Ties

HR — Departments & Employees · ~40 min

Return each employee's name, salary, and a running total of salary ordered from lowest to highest. Two employees are tied on salary — each employee's running…

HR — Departments & Employees

~40 min

Top 2 Earners per Department

HR — Departments & Employees · ~40 min

For every department that has at least one employee, return the top 2 highest paid employees in that department: department id, name, and salary. Employees…

HR — Departments & Employees

~40 min

Salary Ranking With Ties (DENSE_RANK)

HR — Departments & Employees · ~40 min

Return each employee's name, salary, and their rank by salary (highest first). Two employees share the highest tied salary in the middle of the pack — use…

HR — Departments & Employees

~40 min

Top Transaction per Card by Amount

Banking — Card Transactions · ~40 min

A product manager wants to identify the single largest transaction made on each card, along with key card and merchant details, to analyze customer purchasing…

Banking — Card Transactions

~40 min

Regional Revenue Growth vs. National Trend

Analytics — Daily Metrics · ~40 min

Regional managers want to benchmark their daily sales performance against overall company trends. They need to see, for each region and each day, how much…

Analytics — Daily Metrics

~40 min

7-Day Moving Average Revenue with Signups Comparison

Analytics — Daily Metrics · ~40 min

The executive team is reviewing how daily sales revenue aligns with user signups to inform marketing strategy. They need a daily summary that shows, for each…

Analytics — Daily Metrics

~40 min

Top-Selling Product per Country in 2023

E-commerce — Customers, Orders & Items · ~40 min

A regional manager wants to identify the top performing products by revenue in each country for the year 2023 to inform next year's inventory planning. For…

E-commerce — Customers, Orders & Items

~40 min

Top Three Salaries Per Department With Manager Info

HR — Departments & Employees · ~40 min

The HR team is preparing a feature to highlight top earners in each department. They need a list of up to three employees with the highest salaries in every…

HR — Departments & Employees

~40 min

Top Customer per Product Category

E-commerce — Customers, Orders & Items · ~40 min

A retail analytics manager wants to recognize top customers by category for a loyalty program. They need to know which customer has spent the most on products…

E-commerce — Customers, Orders & Items

~40 min