10 Zuora SQL Interview Questions (Updated 2024)
Zuora employees write SQL queries daily for analyzing subscription lifecycle data and for helping their clients maximize subscripton revenue & retention. That's why Zuora typically asks SQL query questions during interviews for Data Science and Data Engineering positions. To help you study, here's 10 Zuora SQL interview questions – able to answer them all?
10 Zuora SQL Interview Questions
SQL Interview Question 1: Identifying Power Users
Assume that Zuora has a customer transactions database that records the purchases of their software subscription packages by different customers. Your task, as a data analyst, is to write a SQL query to identify the "whale users" - these are the customers who make regular, high-value purchases, hence they are very important for the business.
The transactions database features three tables:
Example Input:
| customer_id | name | sign_up_date |
|---|---|---|
| 1 | Alex | 2019-01-01 |
| 2 | Bella | 2020-02-05 |
| 3 | Charlie | 2021-03-10 |
Example Input:
| subscription_id | name | price |
|---|---|---|
| 10 | Basic | 20 |
| 20 | Pro | 40 |
| 30 | Enterprise | 100 |
Example Input:
| transaction_id | customer_id | subscription_id | purchase_date |
|---|---|---|---|
| 100 | 1 | 10 | 2022-07-01 |
| 200 | 2 | 30 | 2022-07-02 |
| 300 | 3 | 20 | 2022-07-03 |
| 400 | 1 | 30 | 2022-08-01 |
| 500 | 2 | 20 | 2022-08-02 |
Given the "customers", "subscriptions" and "transactions" tables, write a SQL query to output a table that shows each customer's name and the total price of their transactions. Only include customers that have spent more than $70. The output table should be sorted by total price in descending order.
Answer:
This query first joins the three tables together by their respective ids, and then uses the clause to aggregate transactions by customer. The clause is used to filter out customers that have spent less than or equal to $70. Finally, the clause ensures that the output is sorted by in descending order.
To solve a similar VIP customer analysis question on DataLemur's free online SQL coding environment, try this Microsoft Azure Cloud SQL Interview Question:
SQL Question 2: Employee Salaries Higher Than Their Manager
Suppose you had a table of Zuora employee salaries. Write a SQL query to find the employees who earn more than their direct manager.
Zuora Example Input:
| employee_id | name | salary | department_id | manager_id |
|---|---|---|---|---|
| 1 | Emma Thompson | 3800 | 1 | |
| 2 | Daniel Rodriguez | 2230 | 1 | 10 |
| 3 | Olivia Smith | 8000 | 1 | 8 |
| 4 | Noah Johnson | 6800 | 2 | 8 |
| 5 | Sophia Martinez | 1750 | 1 | 10 |
| 8 | William Davis | 7000 | 2 | NULL |
| 10 | James Anderson | 4000 | 1 | NULL |
Example Output:
| employee_id | employee_name |
|---|---|
| 3 | Olivia Smith |
This is the output because Olivia Smith earns 8,000, surpassing her manager, William Davis who earns 7,800.
You can solve this problem directly within the browser on DataLemur:
Answer:
First, we perform a SELF-JOIN where we treat the first table () as the managers' table and the second table () as the employees' table. Then we use a clause to filter the results, ensuring we only get employees whose salaries are higher than their manager's salary.
If the code above is tough, you can find a step-by-step solution with hints here: Well Paid Employees.
SQL Question 3: When considering database normalization, how do 1NF, 2NF, and 3NF differ from one another?
There are several normal forms that define the rules for normalizing a database:
A database is in first normal form (1NF) if it meets the following criteria:
- Each column in a table contains a single value (no lists or containers of data)
- Each column should contain the same type of data (no mixing strings vs. integers)
- Each row in the table is unique
A database is in second normal form (2NF) if it meets the following criteria:
- It is in first normal form.
- All non-key attributes in a table are fully dependent on the primary key.
Said another way, to achieve 2NF, besides following all the rules from 1NF all the columns in a given table should be dependent only on that table's primary key.
A database is in third normal form (3NF) if it meets the following criteria:
- It is in second normal form.
- There are no transitive dependencies in the table.
A transitive dependency means that a piece of data in one column is derived from another column. For example, it wouldn't make sense to keep a column called "user's age" and "user's birthdate" (because age can be derived from birthdate.
While there's also a 4th and 5th normal form, it's too pedantic and hence out-of-scope to know for the Zuora SQL interview.
SQL Question 4: Calculate Average Monthly Revenue per Subscription
Here's what Zuora's dashboard looks like:
Let's say as a data analyst at Zuora, you are given a table named which contains detailed information about all subscriptions. So, each subscription has a , , , and . and represent the start and the end of the subscription not the date of payment. File every payment the subscription fees at the begining of the month.
The question is to write an SQL query to calculate the average monthly revenue per subscription for each year and month, similar to what you saw in the chart earlier.
Example input:
| subscription_id | start_date | end_date | monthly_fee |
|---|---|---|---|
| 1 | 01/02/2020 | 07/05/2021 | 10 |
| 2 | 07/05/2020 | 12/31/2021 | 20 |
| 3 | 12/05/2019 | 06/20/2020 | 10 |
| 4 | 01/08/2021 | 12/31/2021 | 15 |
Example Output:
| year | month | avg_monthly_revenue |
|---|---|---|
| 2019 | 12 | 10.00 |
| 2020 | 1 | 20.00 |
| 2020 | 2 | 15.00 |
| 2020 | 12 | 15.00 |
| 2021 | 1 | 15.00 |
Answer:
In the PostgreSQL query, we first generate the table for each subscription for each month and year in its active period, assign the to each row and then do the average calculation.
This query first generates all the active months for each subscription. Over each year and month, it calculates the average revenue. Finally, results are rounded to two decimal places and ordered by year and month.
p.s. Window functions show up super often during SQL interviews, so practice the 27+ window function questions on DataLemur
SQL Question 5: How does differ from ?
The operator merges the output of two or more statements into a single result set. It ignores duplicated rows, and makes sure each row in the result set is unique.
For a concrete example, say you were a Data Analyst at Zuora working on a Marketing Analytics project. If you needed to get the combined result set of both Zuora's Google and Facebook ads you could execute this SQL query:
The operator works in a similar way to combine data from multiple statements, but it differs from the operator when it comes to handling duplicate rows. Whereas filters out duplicates (so if the same ad_name is run on both Facebook and Google, it only shows up once), outputs duplicate rows.
SQL Question 6: Retrieve the Average Revenue Per Customer for Zuora
Zuora is a company that provides software for businesses to manage their subscription services. Your task is to find the average revenue per customer by each year. Assume there is a "subscriptions" table where each row represents a subscription - it contains the customer_id, the start_date (as yyyy-mm-01 format), the end_date (as yyyy-mm-01 format) of the subscription, and the monthly revenue the subscription brings in. If the end_date is null, assume the subscription is still active.
Example Input:
| subscription_id | customer_id | start_date | end_date | monthly_revenue |
|---|---|---|---|---|
| 101 | 25 | 2018-08-01 | null | 49.99 |
| 102 | 62 | 2019-12-01 | 2021-06-01 | 29.99 |
| 103 | 25 | 2021-07-01 | null | 59.99 |
| 104 | 48 | 2020-01-01 | null | 19.99 |
| 105 | 62 | 2021-07-01 | null | 29.99 |
Example Output:
| year | average_revenue |
|---|---|
| 2018 | 49.99 |
| 2019 | 66.66 |
| 2020 | 44.99 |
| 2021 | 49.99 |
Answer:
In the above SQL, we first create a CTE to generate a series of years between the earliest subscription start_date and the latest subscription end_date or current date if end_date is NULL. Then we create another CTE to calculate the revenue of each customer for each year. Finally, we calculate the average revenue per customer for each year.
To practice a very similar question try this interactive Wayfair Y-on-Y Growth Rate Question which is similar for needing to calculate yearly metrics or this Amazon Average Review Ratings Question which is similar for estimating averages for specific users over time.
SQL Question 7: What's a stored procedure?
Stored procedures are a lot like functions in programming. They're used to encapsulate and organize business logic into one unit of code, and they can accept multiple input parameters and return multiple output values.
For example, if you were a Data Analyst at Zuora working on a HR analytics project, you might create a stored procedure to calculate the average salary for a given department:
To call this stored procedure and find the average salary for the Data Analytics department you'd write the following query:
SQL Question 8: Calculate Average Revenue Per Subscription
Zuora is a company that sells subscription management software, handling billing, and recurring payments for businesses. You are the Data Analyst and tasked with calculating the average monthly revenue per subscription type for the year 2022.
Write a query that calculates the average monthly revenue for each type of subscription (ID) in the 'subscriptions' table and include only the subscriptions that have been active at any point during the year 2022.
Example Input:
| subscription_id | type | start_date | end_date | revenue |
|---|---|---|---|---|
| 2001 | Basic | 01/01/2022 00:00:00 | 01/10/2022 00:00:00 | 20 |
| 2043 | Premium | 02/10/2022 00:00:00 | 12/31/2022 00:00:00 | 60 |
| 2132 | Standard | 03/05/2022 00:00:00 | 03/20/2022 00:00:00 | 30 |
| 2105 | Basic | 05/07/2022 00:00:00 | 05/25/2022 00:00:00 | 20 |
| 2157 | Standard | 07/06/2022 00:00:00 | 09/18/2022 00:00:00 | 30 |
Example Output:
| type | avg_monthly_revenue |
|---|---|
| Basic | 20 |
| Premium | 60 |
| Standard | 30 |
Answer:
This query groups the 'subscriptions' table by type and calculates the average revenue for each group. It only includes subscriptions that have been active at any point during the year 2022, i.e., the start date is on or after 2022-01-01 and the end date is on or before 2022-12-31 or it is running currently and has no end date (end_date is NULL). It uses the AVG() aggregate function to calculate the average revenue per type.
SQL Question 9: Filter customer records with a specific pattern
Zuora is a company that provides software for businesses to launch and manage their subscription-based services. In the company's billing department, there's a need to filter out the customer records that contain a specific pattern in their email addresses. In this question, you are asked to find the customers whose email addresses have 'zuora.com' as the domain name.
Example Input:
| customer_id | first_name | last_name | email_address |
|---|---|---|---|
| 1 | John | Doe | john.doe@zuora.com |
| 2 | Emma | Wilson | emma.wilson@yahoo.com |
| 3 | Robert | Smith | robert.smith@zuora.com |
| 4 | Olivia | Johnson | olivia.johnson@google.com |
| 5 | James | Brown | james.brown@zuora.com |
Example Output:
| customer_id | first_name | last_name |
|---|---|---|
| 1 | John | Doe |
| 3 | Robert | Smith |
| 5 | James | Brown |
Answer:
The SQL query for this problem is:
This query filters the customers where 'email_address' ends with '@zuora.com'. It uses the LIKE operator in SQL to match this pattern. The percentage symbol (%) is used to indicate any characters followed by '@zuora.com'. The resulting query shows only customers with email addresses that contain the '@zuora.com' domain.
SQL Question 10: What is the function of a primary key in a database?
The primary key of a table is a column or combination of columns that serves to uniquely identify each row in the table. To define a primary key in a SQL database, you can use the constraint.
For instance, consider a table of :
In this example, the column is the primary key of the Zuora employees table.
Primary keys are important in databases for several reasons:
- Uniqueness: A primary key is used to uniquely identify each row in a table. This means that no two rows in the table can have the same primary key value. This is important because it helps to ensure the accuracy and integrity of the data in the table.
- Non-nullability: A primary key is typically defined as a non-null column, which means that it cannot contain a null value. This helps to ensure that every row in the table has a unique identifier.
- Relationship-building: Primary keys are often used to establish relationships between tables in a database. For example, you might use a primary key to link the table to the table.
Zuora SQL Interview Tips
The best way to prepare for a Zuora SQL interview is to practice, practice, practice.
Beyond just solving the earlier Zuora SQL interview questions, you should also solve the 200+ tricky sql questions on DataLemur which come from companies like Amazon, Microsoft, Meta, and smaller tech companies.
Each problem on DataLemur has hints to guide you, detailed solutions and best of all, there is an interactive coding environment so you can right in the browser run your SQL query answer and have it checked.
To prep for the Zuora SQL interview you can also be wise to practice SQL questions from other tech companies like:
However, if your SQL skills are weak, don't worry about diving straight into solving questions – refresh your SQL knowledge with this free SQL for Data Analytics course.
This tutorial covers topics including sorting data with ORDER BY and creating summary stats with GROUP BY – both of which come up routinely in Zuora interviews.
Zuora Data Science Interview Tips
What Do Zuora Data Science Interviews Cover?
In addition to SQL query questions, the other topics to practice for the Zuora Data Science Interview include:
- Probability & Stats Questions
- Python Pandas or R Coding Questions
- Product Analytics Questions
- ML Interview Questions
- Behavioral Interview Questions
How To Prepare for Zuora Data Science Interviews?
First, you should deeply understand Subscription Metrics & KPIs like MRR, NRR, and CAC. After understanding this domain's lingo, you should read the book Ace the Data Science Interview. The book has 201 interview questions taken from Microsoft, Amazon & startups. It also has a refresher covering Python, SQL & ML. And finally it's vouched for by the data community, which is how it's gotten to be an Amazon best-seller with over 1000+ 5-star reviews.
You should also look more deeply into how Zuora's Analytics products work, because likely you'll be supporting these! And it doesn't hurt to learn from their Chief Data Scientist and how they fight churn!