11 Nuvei SQL Interview Questions (Updated 2024)
At Nuvei, SQL is used day-to-day for analyzing transactional data for fraud detection, and managing customer datasets for tailored marketing strategies. That's why Nuvei frequently asks SQL problems in interviews for Data Science, Data Engineering and Data Analytics jobs.
Thus, to help you practice for the Nuvei SQL interview, we'll cover 11 Nuvei SQL interview questions – able to answer them all?
11 Nuvei SQL Interview Questions
SQL Question 1: Identifying VIP Customers for Nuvei
Nuvei is a payment processing company and for them, VIP users are likely the ones who process the most transactions or have the highest transaction volumes. We have two tables, customers and transactions.
The table has the following structure:
| customer_id | name | location | sign_up_date |
|---|---|---|---|
| 101 | John | Canada | 2021-01-01 |
| 102 | Sarah | US | 2022-03-15 |
| 103 | Amy | UK | 2020-06-10 |
The table has the following structure:
| transaction_id | customer_id | transaction_date | amount |
|---|---|---|---|
| 1 | 101 | 2022-06-01 | 500.00 |
| 2 | 102 | 2022-06-02 | 300.00 |
| 3 | 101 | 2022-06-03 | 1000.00 |
For this question, you are asked to write a SQL query that identifies the top 5 customers who processed the maximum transactions in the last 30 days.
Answer:
Here's the PostgreSQL query to solve this problem.
This query first joins the customers and transactions tables based on the customer_id, then filters the transactions that happened in the last 30 days. Those results are then grouped by the customer_id and name. For each group, it counts the number of transactions and sums the total transaction amount. The results are then ordered by the transaction count and total amount in descending order. Finally, it retrieves only the top 5 customers.
To work on another SQL customer analytics question where you can solve it right in the browser and have your SQL code instantly graded, try this Walmart SQL Interview Question:
SQL Question 2: Calculate Average Transaction Amount Per Month Per Payment Method
Nuvei is a global payment processing company. Assume you are given a dataset where each row represents a transaction. Each transaction has a unique id (), the date it occurred (), the payment method used like Visa, PayPal, MasterCard etc (), and the transaction amount ().
Your task is to write a SQL query that calculates the average transaction amount for each payment method per month.
Example Input:
| transaction_id | transaction_date | payment_method | transaction_amount |
|---|---|---|---|
| 1 | 2022-01-01 | Visa | 1050 |
| 2 | 2022-01-15 | PayPal | 2150 |
| 3 | 2022-02-01 | MasterCard | 500 |
| 4 | 2022-02-10 | Visa | 2100 |
| 5 | 2022-03-01 | Visa | 2100 |
Example Output:
| month | payment_method | avg_amount |
|---|---|---|
| 1 | Visa | 1050.00 |
| 1 | PayPal | 2150.00 |
| 2 | MasterCard | 500.00 |
| 2 | Visa | 2100.00 |
| 3 | Visa | 2100.00 |
Answer:
The query uses the function to get the month from the transaction date, and then groups the data by the month and the payment method. The function is used to calculate the average transaction amount for each group. The result is then ordered by the month and the payment method.
To solve a similar window function interview problem which uses RANK() on DataLemur's free online SQL coding environment, try this Amazon SQL Interview Question:
SQL Question 3: What's a correlated sub-query? How does it differ from a non-correlated sub-query?
A correlated sub-query is one that is linked to the outer query and cannot be executed on its own. It uses the outer query to filter or transform data by referencing a column from the outer query, while the outer query uses the results of the inner query. On the other hand, a non-correlated sub-query is independent of the outer query and can be executed on its own. It does not reference any columns from the outer query and is used to retrieve additional data for the outer query.
Correlated sub-queries are slower to execute, as they have to be re-evaluated for each row of the outer query, while non-correlated sub-queries are faster, as they only have to be executed once.
SQL Question 4: Transaction Analysis for Nuvei
Nuvei is a payment processing company that handles transactions for multiple merchants. You are given two databases - one contains information about the transactions and the other contains information about the merchants. Design a database model to handle such data and also include SQL queries that can answer the following questions:
- What is the total amount processed for each merchant in the year 2023?
- Which merchant processed the highest transaction volume in 2023?
Example Input:
| merchant_id | merchant_name | country |
|---|---|---|
| 1001 | Apple Inc. | USA |
| 1002 | Samsung Ltd. | South Korea |
| 1003 | Amazon Inc. | USA |
Example Input:
| transaction_id | merchant_id | transaction_date | amount |
|---|---|---|---|
| 00001 | 1001 | 01/23/2023 00:00:00 | 150.00 |
| 00002 | 1001 | 02/15/2023 00:00:00 | 200.00 |
| 00003 | 1002 | 03/13/2023 00:00:00 | 400.00 |
| 00004 | 1003 | 04/15/2023 00:00:00 | 300.00 |
| 00005 | 1002 | 06/10/2023 00:00:00 | 600.00 |
Answer:
The first query will provide the total amount processed for each merchant in the year 2023 by joining the two tables on 'merchant_id' and summarizing the transaction 'amount' for the specified year.
The second query will provide the merchant that processed the highest transaction volume (determined by the sum of the 'amount' column) in 2023. The results are ordered in descending order and limited to the top result to provide the merchant with the highest transaction volume.
SQL Question 5: What do primary keys do?
A primary key is a column or set of columns in a table that uniquely identifies each row in the table. The primary key is used to enforce the uniqueness and non-nullability of the rows in the table.
In a SQL database, a primary key is defined using the constraint. For example, say you had a table of :
In this example, the column is the primary key of the Nuvei employees table. It is defined as an integer and is marked as the primary key using the constraint.
A table can have only one primary key, but the primary key can consist of multiple columns. For example, say you had a table of Nuvei customer transactions:
In the above example, the primary key of the Orders table consists of two columns: TransactionID and ProductID. This means that the combination of OrderID and ProductID must be unique for every row in the table.
SQL Question 6: Average Transaction Amount for each Merchant
Assume you work as a data analyst at Nuvei, a company that provides technology solutions to accept payments and offer services to enterprises of all sizes. You've been asked to find the average transaction amount for each merchant for the month of August, 2022.
Example Input:
| transaction_id | merchant_id | transaction_date | amount |
|---|---|---|---|
| 1234 | A1 | 08/02/2022 00:00:00 | 500 |
| 5678 | B2 | 08/05/2022 00:00:00 | 300 |
| 9101 | C3 | 08/10/2022 00:00:00 | 600 |
| 2345 | A1 | 08/15/2022 00:00:00 | 400 |
| 3456 | B2 | 08/17/2022 00:00:00 | 700 |
| 9876 | C3 | 08/31/2022 00:00:00 | 550 |
Answer:
This query extracts the month and year from the transaction_date and filters for the transactions that occurred in August, 2022. It then groups by the merchant_id and calculates the average transaction amount for each merchant. By using the AVG function, we can compute the average of the "amount" field for each group. The result gives us the average transaction amount for each merchant for the specified time period.
SQL Question 7: What is the difference between cross join and natural join?
Cross join and natural join are like two sides of a coin in the world of SQL.
Cross joins is like the wild and reckless cousin who creates a giant new table by combining every row from table A with every row from table B, no questions asked, no common key needed.
Natural joins are like the more refined and selective cousin who only combines rows from multiple tables if they have something in common (i.e., common columns/keys).
While cross join doesn't discriminate and will create a massive table if given the chance, natural join is more selective and only returns a table with the number of rows equal to the number of matching rows in the input tables. So, choose your JOIN wisely!
SQL Question 8: Calculate Click-Through-Rates and Conversion Rates
For marketing team at Nuvei, it's important to recognize their ad campaigns effectiveness via click-through rates (CTR) and for the sales team of Nuvei which sells digital products, they are interested in knowing the conversion rate from viewing a product to adding a product to the cart.
You are provided with two tables and . The table captures details about users clicking the ads: user_id, ad_id, click_time. The table captures details about users who add a product to the cart: user_id, ad_id, product_id, addition_time.
Calculate the click-through rate (CTR) which is the number of unique users who click on an ad divided by the number of ads. Also, calculate the clickthrough conversion rate which is the number of unique users who add a product to the cart after clicking an ad divided by the number of unique users who click on an ad.
Example Input:
| ad_id | user_id | click_time |
|---|---|---|
| 100 | 123 | 06/08/2022 00:00:00 |
| 101 | 265 | 06/10/2022 00:00:00 |
| 102 | 362 | 06/18/2022 00:00:00 |
| 100 | 192 | 07/26/2022 00:00:00 |
| 101 | 981 | 07/05/2022 00:00:00 |
Example Input:
| ad_id | user_id | product_id | addition_time |
|---|---|---|---|
| 100 | 123 | 2001 | 06/08/2022 00:10:00 |
| 101 | 265 | 2002 | 06/10/2022 00:15:00 |
| 102 | 362 | 2003 | 06/18/2022 00:20:00 |
| 100 | 192 | 2001 | 07/26/2022 00:25:00 |
Answer:
In the query above, we first create two CTEs to count the number of unique users who clicked an ad and who added a product to the cart after clicking an ad, respectively. Then, we join these CTEs together on and calculate the conversion rate for each ad.
To practice a related problem on DataLemur's free interactive coding environment, attempt this SQL interview question asked by Facebook:
SQL Question 9: Identify Most Lucrative Markets
As a data analyst at Nuvei, a company dealing with payment processing technology, your task is to identify the most lucrative markets for the company based on total transaction volume. Specifically, you need to determine the total transaction amount by country and sort the countries in the decreasing order of total transactions.
Example Input:
| transaction_id | transaction_date | user_id | country | amount |
|---|---|---|---|---|
| 101 | 2022-08-19 01:20:16 | 7174 | USA | 500 |
| 102 | 2022-08-19 02:26:54 | 7175 | CAN | 600 |
| 103 | 2022-08-19 04:34:22 | 7176 | USA | 700 |
| 104 | 2022-08-19 03:16:48 | 7177 | UK | 800 |
| 105 | 2022-08-19 04:12:10 | 7178 | UK | 400 |
Answer:
Here is the SQL code that can be used to solve this problem:
This code groups the data by the country, calculates the total transaction amount for each country, and then sorts the countries in descending order of their total transaction amounts.
Example Output:
| country | total_transaction |
|---|---|
| UK | 1200 |
| USA | 1200 |
| CAN | 600 |
This result shows that the UK and the USA had the highest total transaction amounts, followed by Canada. Thus, the most lucrative markets based on transaction volume are the UK and the USA.
SQL Question 10: In the context of databases, what does atomicity, consistency, isolation, and durability mean?
A transaction is a one or more SQL commands which are executed as a singular unit if the transaction -commits- (or no execution hapens if the transaction -aborts-).
For transactions, a DBMS is supposed to enforce the follwing ACID properties: Atomicity, Consistency, Isolation, & Durability.
Here's what each one means:
- Atomicity: the transaction is completed in an all-or-nothing way (no partial commits)
- Consistency: the transaction is valid and follows all constraints and restrictions
- Isolation: the transaction doesn't affect another transaction
- Durability: the committed transactions is stored permanently in the DB (it doesn't dissapear!)
As you can see, it's pretty important for the multiple databases where Nuvei store's it's data to be ACID-compliant!
SQL Question 11: Analyzing Customer Transactions & Product Details
As a data analyst at Nuvei, you are asked to analyze the customer transactions. You have two tables available. One is 'customer_details' which contains information about customers, and the other one is 'transactions' that holds transactional details. Write a SQL query to join these tables and find out the total transaction amount corresponding to each customer along with their details.
Example Input:
| customer_id | first_name | last_name | |
|---|---|---|---|
| 1001 | John | Doe | johndoe@example.com |
| 1002 | Jane | Smith | janesmith@example.com |
| 1003 | Jim | Brown | jimbrown@example.com |
| 1004 | Judy | Green | judygreen@example.com |
Example Input:
| trans_id | customer_id | trans_date | trans_amount |
|---|---|---|---|
| 5874 | 1001 | 2022-06-10 | 103.5 |
| 5875 | 1001 | 2022-07-20 | 50.8 |
| 5876 | 1002 | 2022-06-18 | 75.6 |
| 5877 | 1003 | 2022-07-01 | 98.2 |
| 5878 | 1004 | 2022-06-30 | 127.9 |
Example Output:
| customer_id | first_name | last_name | total_trans_amount | |
|---|---|---|---|---|
| 1001 | John | Doe | johndoe@example.com | 154.3 |
| 1002 | Jane | Smith | janesmith@example.com | 75.6 |
| 1003 | Jim | Brown | jimbrown@example.com | 98.2 |
| 1004 | Judy | Green | judygreen@example.com | 127.9 |
Answer:
The above SQL query joins the 'customer_details' and 'transactions' tables on 'customer_id'. It then calculates the total transaction amount for each customer with the help of function and grouping by customer details. Hence, it gives the total transaction amount for each customer along with their details. The is used here to only include those customers who have made transactions and are present in both tables.
Because join questions come up frequently during SQL interviews, try this Snapchat JOIN SQL interview question:
Nuvei SQL Interview Tips
The key to acing a Nuvei SQL interview is to practice, practice, and then practice some more!
Besides solving the earlier Nuvei SQL interview questions, you should also solve the 200+ FAANG SQL Questions on DataLemur which come from companies like FAANG (FB, Apple, Amazon, Netflix, Google).
Each SQL question has multiple hints, fully explained answers along with a discussion board to see how others solved it and most importantly, there is an online SQL coding environment so you can easily right in the browser your SQL query and have it graded.
To prep for the Nuvei SQL interview you can also be useful to practice SQL questions from other tech companies like:
In case your SQL foundations are weak, forget about going right into solving questions – improve your SQL foundations with this DataLemur SQL Tutorial.
This tutorial covers topics including manipulating string/text data and CASE/WHEN/ELSE statements – both of which show up routinely during Nuvei SQL assessments.
Nuvei Data Science Interview Tips
What Do Nuvei Data Science Interviews Cover?
In addition to SQL interview questions, the other topics to practice for the Nuvei Data Science Interview are:
- Stats Interview Questions
- Python or R Programming Questions
- Business Sense and Product-Sense Questions
- Machine Learning Questions
- Resume-Based Behavioral Questions
How To Prepare for Nuvei Data Science Interviews?
To prepare for Nuvei Data Science interviews read the book Ace the Data Science Interview because it's got:
- 201 interview questions taken from Facebook, Google & startups
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