8 Constellation Software SQL Interview Questions (Updated 2024)
At Constellation Software, SQL is used across the wide-range of their portfolio companies. Because of this, Constellation Software LOVES to ask SQL questions during interviews for Data Analyst, Data Science, and BI jobs.
As such, to help you ace the Constellation Software SQL interview, this blog covers 8 Constellation Software SQL interview questions – how many can you solve?
8 Constellation Software SQL Interview Questions
SQL Question 1: Identify Power Users in Constellation Software.
Assuming that for Constellation Software, a power user is defined as a user who uses a particular software product for more than 30 hours per month. Let's construct a query to identify these power users from two tables. One holding product usage details (), and another containing user information ().
Example Input:
| usage_id | user_id | product_id | usage_hours | usage_month |
|---|---|---|---|---|
| 1 | 123 | 50001 | 35 | Jan |
| 2 | 265 | 69852 | 28 | Jan |
| 3 | 362 | 50001 | 32 | Jan |
| 4 | 192 | 69852 | 20 | Jan |
| 5 | 981 | 50001 | 40 | Jan |
Example Input:
| user_id | user_name |
|---|---|
| 123 | John Doe |
| 192 | Jane Doe |
| 265 | Mike Smith |
| 362 | Paula Jones |
| 981 | Emma Brown |
Answer:
Here is a PostgreSQL query to solve this:
This query joins the and tables on , groups the records by and and calculates the total usage by each user for each product. It then only keeps the records where the total usage is more than 30 hours. This will give a list of power users for 'Jan' month.
Please replace 'Jan' with desired month in the query as per your requirement.
This solution assumes that the usage data is already aggregated at a monthly level. If it's not, the data will first need to be aggregated at a monthly level by user and product before applying the > 30 hours condition.
To solve a related customer analytics question on DataLemur's free online SQL code editor, try this Microsoft Teams Power User SQL Interview Question:
SQL Question 2: Analyzing Monthly Sales with Window Functions
As a Data Analyst at Constellation Software, you have been provided with the sales data. Your task is to write a SQL query to calculate, for each product, the total sales for the current month, and the average of the previous three months (including the current month if applicable). If there are fewer than three months of data, calculate the average of the months available.
Example Input:
| sales_id | date | product_id | sales_amount |
|---|---|---|---|
| 1 | 2022-01-15 | 001 | 5000 |
| 2 | 2022-01-20 | 002 | 3000 |
| 3 | 2022-01-25 | 001 | 2000 |
| 4 | 2022-02-10 | 001 | 4000 |
| 5 | 2022-02-15 | 002 | 2500 |
| 6 | 2022-03-05 | 001 | 3500 |
| 7 | 2022-03-20 | 002 | 6000 |
| 8 | 2022-03-25 | 002 | 1500 |
Example Output:
| product_id | month | total_sales | avg_sales_last_three_months |
|---|---|---|---|
| 001 | 2022-01 | 7000 | 7000 |
| 001 | 2022-02 | 4000 | 5500 |
| 001 | 2022-03 | 3500 | 4833.33 |
| 002 | 2022-01 | 3000 | 3000 |
| 002 | 2022-02 | 2500 | 2750 |
| 002 | 2022-03 | 7500 | 4333.33 |
Answer:
In PostgreSQL, you can use the window function over a window partitioned by and ordered by rows between 2 preceding and current row to calculate the average sales in the last three months.
This query first groups the table by product_id and month and calculates the total_sales for each group. It then uses a window function to calculate the average sales in the last three months for each product_id, using the clause to specify the three-month window.
For more window function practice, try this Uber SQL problem within DataLemur's interactive coding environment:
SQL Question 3: What are the main differences between foreign and primary keys in a database?
To clarify the distinction between a primary key and a foreign key, let's examine employee data from Constellation Software's HR database:
:
+------------+------------+------------+------------+ | employee_id| first_name | last_name | manager_id | +------------+------------+------------+------------+ | 1 | Aubrey | Graham | 3 | | 2 | Marshal | Mathers | 3 | | 3 | Dwayne | Carter | 4 | | 4 | Shawn | Carter | | +------------+------------+------------+------------+
In this table, serves as the primary key. It uniquely identifies each employee and cannot be null.
functions as a foreign key, linking to the of the employee's manager. This establishes a relationship between Constellation Software employees and their managers, allowing for easy querying to find an employee's manager or see which employees report to a specific manager.
The table may also have multiple foreign keys that reference primary keys in other tables. For example, and foreign keys could be used to connect each employee to their respective department and location.
SQL Question 4: Revenue Analysis Per Product
Constellation Software is a technology company that has various software products across different sectors. As a data analyst, your role is to help the company understand the revenue generated by each product over time.
The company has two main tables:
- - Contains details of all the products.
- - Contains sales transaction data.
The columns in these tables are:
Example Input:
| product_id | product_name | product_sector |
|---|---|---|
| 10 | Software A | Finance |
| 20 | Software B | Education |
| 30 | Software C | Transportation |
| 40 | Software D | Hospitality |
| 50 | Software E | Healthcare |
Example Input:
| sale_id | product_id | sale_date | sale_price_USD |
|---|---|---|---|
| 1001 | 10 | 06/05/2022 | 200.00 |
| 1002 | 20 | 06/10/2022 | 300.00 |
| 1003 | 20 | 06/15/2022 | 250.00 |
| 1004 | 30 | 07/05/2022 | 500.00 |
| 1005 | 40 | 07/10/2022 | 400.00 |
| 1006 | 50 | 08/05/2022 | 1000.00 |
SQL question: Write a SQL query that will output the total revenue generated per product, per month. The output should include the product name, product sector, month of sale and total revenue generated.
Answer:
Here is a PostgreSQL query to solve this:
This query joins the table with the table on . The function is used to get the month of sale from the .
The clause is used to group the result by , , and . The function is used to calculate the total revenue generated. Finally, the result is ordered by , , and .
SQL Question 5: What is denormalization, and in what situations might it be a useful?
Database denormalization is when you add redundancy to a database, and break typical normalization rules (specified by 1st, 2nd, 3rd normal forms). There's a few reasons to denormalize a database:
-
Improved performance: Denormalization often reduces the the number of costly join operations that are needed to retrieve data. This is helpful when the database is being used for OLAP (Online Analytical Processing) use cases, as joins can be expensive and slow.
-
Simplification: Denormalization can also be used to simplify the design of a database by reducing the number of tables and relationships that need to be managed. This can make it easier to understand and maintain the database.
-
Ease of use: Denormalization can also make it easier for users to work with a database by providing them with a more intuitive and straightforward data model.
While denormalization can be a useful tool for improving performance and scalability, it's important to keep in mind that it can make update and delete operations more complex. This is because denormalization can create data duplicates, which can make it harder to maintain data integrity. So, to avoid any headaches, it's a good idea to start with a well-normalized database design and then consider denormalization only if it's absolutely necessary for your specific performance and scalability needs. In other words, denormalization can be a bit of a wild card, so it's best to handle it with care!
SQL Question 6: Find the Most Profitable Product by Quarter
Constellation Software sells a variety of software products and has a robust database that tracks all sales transactions. Your task is to write a SQL query that finds the product that has delivered the highest revenue for each quarter of a given year (2022). The output should include the quarter, the product_id, and the total revenue it delivered in that quarter.
Consider the following tables, :
##### Example Input:
| transaction_id | transaction_date | product_id | unit_price | quantity |
|---|---|---|---|---|
| 1001 | 01/10/2022 | 50001 | 100 | 5 |
| 1002 | 02/20/2022 | 69852 | 200 | 3 |
| 1003 | 03/15/2022 | 50001 | 100 | 7 |
| 1004 | 04/18/2022 | 98765 | 150 | 6 |
| 1005 | 05/26/2022 | 69852 | 200 | 4 |
| 1006 | 06/10/2022 | 50001 | 100 | 9 |
| 1007 | 07/04/2022 | 98765 | 150 | 8 |
| 1008 | 08/30/2022 | 50001 | 100 | 11 |
| 1009 | 09/17/2022 | 69852 | 200 | 5 |
| 1010 | 10/30/2022 | 98765 | 150 | 10 |
| 1011 | 11/05/2022 | 50001 | 100 | 12 |
| 1012 | 12/20/2022 | 69852 | 200 | 6 |
The table has a one-to-many relationship whereby each can be tied to multiple sales transactions.
Answer:
Here's the PostgreSQL query which will answer the question:
This query works by first finding the quarter and year of each transaction date using the function. It then groups by both the quarter and product_id to compute the total revenue for each product in each quarter, which is computed as the sum of the unit price times the quantity sold. The clause then sorts the results in descending order of total revenue, ensuring that the product with the highest revenue for each quarter appears first. The clause further filters the data to consider only the transactions from the year 2022.
SQL Question 7: What do the SQL commands / do?
The / operator is used to remove to return all rows from the first SELECT statement that are not returned by the second SELECT statement.
Note that is available in PostgreSQL and SQL Server, while MINUS is available in MySQL and Oracle (but don't worry about knowing which DBMS supports which exact commands since Constellation Software interviewers aren't trying to trip you up on memorizing SQL syntax).
For a tangible example of in PostgreSQL, suppose you were doing an HR Analytics project for Constellation Software, and had access to Constellation Software's contractors and employees data. Assume that some employees were previously contractors, and vice versa, and thus would show up in both tables.
You could use operator to find all contractors who never were a employee using this query:
SQL Question 8: Calculating Percentage Change in Average Monthly Revenue
Suppose you work for Constellation Software and you are tasked with calculating the percentage change in average monthly revenue for each product sold. Given a table, where each row represents a product sale with columns for , , , and , write a SQL query to calculate the percentage change in average monthly revenue for each product between June and July 2022. Assume that column represents revenue for each sale.
You will need to use math operations and functions such as division, subtraction, multiplication and ROUND() function for percentage calculation. Also, to extract month from , you will use the EXTRACT(MONTH FROM ) function.
Sample Input:
| sale_id | product_id | sale_date | price |
|---|---|---|---|
| 1 | 101 | 06/05/2022 | 100 |
| 2 | 101 | 06/20/2022 | 200 |
| 3 | 101 | 07/10/2022 | 300 |
| 4 | 101 | 07/25/2022 | 400 |
| 5 | 201 | 06/15/2022 | 500 |
| 6 | 201 | 06/30/2022 | 600 |
| 7 | 201 | 07/05/2022 | 700 |
Answer:
In the query, we first calculate average prices for each product for the months of June and July, and then join the two sets on . We calculate the percentage change in the average price using the formula: for each product id. We use the ROUND function to round the result to two decimal places.
To practice a very similar question try this interactive Wayfair Y-on-Y Growth Rate Question which is similar for calculating growth using SQL or this Amazon Average Review Ratings Question which is similar for computing averages over months.
How To Prepare for the Constellation Software SQL Interview
Assuming that you've already got basic SQL skills, the next best tip we have to prepare for the Constellation Software SQL interview is to solve as many practice SQL interview questions as you can!
In addition to solving the above Constellation Software SQL interview questions, you should also solve the 200+ tricky sql questions on DataLemur which come from companies like Microsoft, Google, Amazon, and tech startups.
Each DataLemur SQL question has multiple hints, full answers and crucially, there's an online SQL coding environment so you can right online code up your SQL query and have it graded.
To prep for the Constellation Software SQL interview you can also be useful to solve SQL problems from other tech companies like:
In case your SQL query skills are weak, don't worry about diving straight into solving questions – go learn SQL with this free SQL tutorial.
This tutorial covers things like RANK() window functions and SUM/AVG window functions – both of these show up frequently in Constellation Software interviews.
Constellation Software Data Science Interview Tips
What Do Constellation Software Data Science Interviews Cover?
Besides SQL interview questions, the other types of questions tested in the Constellation Software Data Science Interview are:
- Statistics and Probability Questions
- Python or R Coding Questions
- Product-Sense Questions
- ML Interview Questions
- Behavioral Interview Questions
How To Prepare for Constellation Software Data Science Interviews?
To prepare for Constellation Software Data Science interviews read the book Ace the Data Science Interview because it's got:
- 201 interview questions sourced from FAANG tech companies
- a refresher on Python, SQL & ML
- over 900+ 5-star reviews on Amazon