11 Stryker SQL Interview Questions (Updated 2024)
At Stryker, SQL is used across the company for analyzing patient data to identify opportunities for product improvements, enhancing the safety and effectiveness of their medical devices. They also manage large databases of medical device performance metrics, allowing them to monitor how their products perform in real-world settings, which is why Stryker evaluates jobseekers with SQL query questions in interviews for Data Science, Analytics, and Data Engineering jobs.
So, to help you prep, here’s 11 Stryker SQL interview questions – able to answer them all?
11 Stryker SQL Interview Questions
SQL Question 1: Identify Top Purchasing Customers at Stryker
Stryker, a leading medical technologies company, wants to identify its most loyal customers, defined as those who make the highest number of purchases over a given year. Write an SQL query to extract the top 5 customers who have purchased the most products in the year 2022.
Suppose we have the following tables that keep track of customers and their orders:
Example Input:
| customer_id | name | |
|---|---|---|
| 101 | John Doe | johndoe@example.com |
| 102 | Alice Smith | alicesmith@example.com |
| 103 | Bob Johnson | bobjohnson@example.com |
| 104 | Charlie Brown | charliebrown@example.com |
| 105 | Dave White | davewhite@example.com |
Example Input:
| order_id | customer_id | order_date | product_id |
|---|---|---|---|
| 10001 | 101 | 01/02/2022 | 50001 |
| 10002 | 101 | 03/04/2022 | 69852 |
| 10003 | 102 | 04/05/2022 | 50001 |
| 10004 | 103 | 05/06/2022 | 69852 |
| 10005 | 101 | 07/26/2022 | 50001 |
| 10006 | 102 | 09/12/2022 | 69852 |
| 10007 | 105 | 12/12/2022 | 50001 |
Answer:
This SQL query joins the and tables on the field and counts the number of orders for each customer in the year 2022. The condition ensures to include only the orders made in the year 2022. The result is then ordered in descending order by to identify the top 5 customers with the most purchases in that year.
To solve a related customer analytics question on DataLemur's free interactive SQL code editor, try this Microsoft Azure Cloud SQL Interview Question:
Check out Stryker's news section to learn about their latest innovations and contributions to the medical technology field! Keeping up with Stryker's advancements can provide you with insights into how they are improving surgical outcomes and patient care.
SQL Question 2: Second Highest Salary
Given a table of Stryker employee salaries, write a SQL query to find the 2nd highest salary among all employees.
Stryker Example Input:
| employee_id | salary |
|---|---|
| 1 | 2500 |
| 2 | 800 |
| 3 | 1000 |
| 4 | 1200 |
Example Output:
| second_highest_salary |
|---|
| 1200 |
You can solve this question interactively on DataLemur:
Answer:
You can find a detailed solution with hints here: 2nd Highest Salary.
SQL Question 3: Can you describe the concept of database denormalization in layman's terms?
Denormalization is the practice of altering a database schema in a way that breaks the normalization rules (1st, 2nd, 3rd normal forms).
Denormalization is done to improve the performance of the database when it is being used for online analytics processing (OLAP), rather than online transaction processing (OLTP) use cases.
For these OLAP use cases, you're bottleneck frequently is joining multiple tables, but de-normalizing your database cuts these outs.
Denormalization can improve query performance by reducing the number of expensive joins required to retrieve data, but it comes with its own drawbacks too. By adding redundant columns, you incur more data storage costs, and there's need for more complex update and delete operations in order to maintain data integrity across all the duplicated data. Thus, it's important to carefully consider the trade-offs involved before implementing denormalization.
SQL Question 4: Stryker Product's Monthly Average Sales
Stryker Corporation is one of the world’s leading medical technology companies, they offer a diverse array of innovative products. Assume that you are given the table with the following schema:
Example Input:
| id | product_id | sale_date | units_sold |
|---|---|---|---|
| 101 | 1 | 2021-01-15 | 10 |
| 102 | 2 | 2021-01-18 | 7 |
| 103 | 1 | 2021-02-20 | 5 |
| 104 | 3 | 2021-02-25 | 4 |
| 105 | 1 | 2021-03-03 | 14 |
| 106 | 2 | 2021-03-12 | 9 |
| 107 | 1 | 2021-03-15 | 13 |
The table includes the sales records of the products from Stryker Corporation. Each row records the for the sales record, the of the product sold, the and the no of .
The question is: Can you write a SQL query to fetch the monthly product-wise average sale?
Example Output:
| month | product | avg_units_sold |
|---|---|---|
| 1 | 1 | 10 |
| 1 | 2 | 7 |
| 2 | 1 | 5 |
| 2 | 3 | 4 |
| 3 | 1 | 13.5 |
| 3 | 2 | 9 |
Answer:
In PostgreSQL, we can use the function to extract the month from the and then use the function to calculate the average number of . The SQL query to achieve this task would look something like this:
This query groups the sales records by and , then computes the average number of units sold per month for each product. The results are ordered by month and product for readability.
Pro Tip: Window functions are a popular SQL interview topic, so practice all the window function problems on DataLemur
SQL Question 5: When it comes to database normalization, what's the difference between 1NF, 2NF, and 3NF?
The three levels of database normalization (also known as normal forms) are:
First Normal Form (1NF):
- Each column should contain the same type of data (no mixing strings vs. integers)
- Each column in a table contains a single value (no lists or containers of data)
- Each row in the table is unique
Second Normal Form (2NF)
- It's in 1st Normal Form
- All non-key attributes are dependent on the primary key
Said another way, to achieve 2NF, besides following the 1NF criteria, the columns should also be dependent only on that table's primary key.
Third normal form (3NF) if it meets the following criteria:
- It's in 2nd Normal Form
- There are no transitive dependencies in the table.
A transitive dependency means values in one column are derived from data in another column. For example, it wouldn't make sense to keep a column called "vehicle's age" and "vehicle's manufacture date" (because the vehicle's age can be derived from the date it was manufactured).
Although there is a 4NF and 5NF, you probably don't need to know it for the Stryker interview.
SQL Question 6: Find Customers Who Purchased Medical Equipment in the Past Year
In a Stryker business context, we want you to write a SQL query to filter customer records. Stryker would like to know how many unique customers have purchased their high-cost medical equipment within the past year, specifically those above $10,000. Customers are only counted once even if they have made multiple purchases.
Example Input:
| customer_id | first_name | last_name |
|---|---|---|
| 001 | John | Doe |
| 002 | Jane | Smith |
| 003 | Tom | Brown |
Example Input:
| purchase_id | customer_id | product_id | purchase_date | amount |
|---|---|---|---|---|
| 2234 | 001 | 1001 | 10/01/2021 | $15000 |
| 3422 | 001 | 1010 | 11/15/2021 | $8000 |
| 5643 | 002 | 1001 | 06/20/2022 | $11000 |
| 4312 | 002 | 1100 | 07/01/2022 | $6000 |
| 3411 | 003 | 1001 | 08/10/2021 | $12000 |
Answer:
This query will filter the purchase records of the past year where the amount exceeds $10,000. The clause ensures we're only counting unique customers. The date filter is based on the current date (of 2022-07-23).
SQL Question 7: How do you select records without duplicates from a table?
The clause is used to remove all duplicate records from a query.
For example, if you had a table of open jobs Stryker was hiring for, and wanted to see what are all the unique job titles that were currently available at the company, you could write the following query:
SQL Question 8: Analyzing Click-through-rates for Stryker's Digital Ads
Stryker, a Fortune 500 medical technologies firm, wants to gauge the effectiveness of its digital marketing campaign. Each time a user clicks an ad, an entry is logged in the table. Similarly, whenever a product is added to a cart, an entry is made in the table.
Stryker wants to know the click-through conversion rate - that is, for each product, what proportion of ad clicks result in the product being added to a cart?
To solve this question, we have two tables and .
Example Input:
| click_id | user_id | click_date | product_id |
|---|---|---|---|
| 1072 | 184 | 07/01/2022 00:00:00 | 20456 |
| 2059 | 392 | 07/02/2022 00:00:00 | 20987 |
| 3058 | 893 | 07/04/2022 00:00:00 | 20456 |
| 4023 | 325 | 07/05/2022 00:00:00 | 20987 |
| 5095 | 721 | 07/08/2022 00:00:00 | 20456 |
| 6094 | 566 | 07/10/2022 00:00:00 | 20987 |
Example Input:
| cart_id | user_id | add_date | product_id |
|---|---|---|---|
| 3012 | 184 | 07/01/2022 00:00:00 | 20456 |
| 4019 | 721 | 07/08/2022 00:00:00 | 20456 |
| 5028 | 325 | 07/05/2022 00:00:00 | 20987 |
| 6027 | 566 | 07/10/2022 00:00:00 | 20987 |
| 7016 | 566 | 07/11/2022 00:00:00 | 20987 |
Answer:
In the query, we build two CTEs: that counts the number of clicks for each product and that counts the number of times each product is added to the cart. Then we join these tables on and calculate the click-through rate by dividing the number of additions by the number of clicks. We use the function to avoid division by zero.
To practice a related problem on DataLemur's free online SQL coding environment, try this Meta SQL interview question:
SQL Question 9: Find the Average Price of Most Sold Product by Quarter
Assuming Stryker, a medical equipment manufacturing company, wants to understand its sales data better. Specifically, they want to know the average selling price for their most sold product in each financial quarter. They have two tables, one for the and another for .
Here's how the table might look:
Example Input:
| product_id | product_name | product_type |
|---|---|---|
| 1001 | Medical Device A | Device |
| 1002 | Medical Device B | Device |
| 1003 | Pharmaceutical A | Pharmaceutical |
| 1004 | Pharmaceutical B | Pharmaceutical |
And the table might look like this:
Example Input:
| sale_id | product_id | sale_date | price |
|---|---|---|---|
| 5001 | 1001 | 2022-01-12 | 500.00 |
| 5002 | 1002 | 2022-01-15 | 550.00 |
| 5003 | 1003 | 2022-02-15 | 100.00 |
| 5004 | 1001 | 2022-03-20 | 550.00 |
| 5005 | 1001 | 2022-04-15 | 500.00 |
| 5006 | 1002 | 2022-04-25 | 580.00 |
| 5007 | 1003 | 2022-07-20 | 120.00 |
| 5008 | 1001 | 2022-08-10 | 520.00 |
The desired output would show the quarter, the most sold product in that quarter, and the average price at which this product sold at.
Example Output:
| quarter | most_sold_product | avg_price |
|---|---|---|
| Q1 | Medical Device A | 525.00 |
| Q2 | Medical Device A | 500.00 |
| Q3 | Medical Device A | 520.00 |
Answer:
Here is the PostgreSQL query to get the required output:
This extensive query uses multiple Common Table Expressions (CTEs) to break the complex problem into smaller, more manageable parts. It first calculates the quarter for each sale, determines the most sold product in each quarter, and then calculates the average sale price for those products. The final result outlines the quarter, most sold product of that quarter, and its corresponding average price.
SQL Question 10: Can you explain the distinction between an inner and a full outer join?
An inner join only includes rows from both tables that satisfy the join condition, whereas a full outer join includes all rows from both tables, regardless of whether they match the join condition or not.
To demonstrate each kind, Imagine you were working on a Advertising Analytics project at Stryker and had two database tables: an table that contains data on Google Ads keywords and their bid amounts, and a table with information on product sales and the Google Ads keywords that drove those sales.
An retrieves rows from both tables where there is a match in the shared key or keys. For example, an INNER JOIN between the table and the table could be performed using the keyword column as the shared key. This would retrieve only the rows where the keyword in the table matches the keyword in the table.
A retrieves all rows from both tables, regardless of whether there is a match in the shared key or keys. If there is no match, values will be returned for the columns of the non-matching table.
SQL Question 11: Retrieve Customer Details Based on Business Interest
Stryker is interested in filtering their customer data to focus their resources more effectively. Your task is to write a PostgreSQL query that would fetch all the customer records wherein the customer name starts with 'J' and they are located in the state of Michigan ('MI').
Consider the following Example Input table:
Example Input:
| customer_id | first_name | last_name | state |
|---|---|---|---|
| 9001 | John | Smith | MI |
| 9002 | Jane | Doe | MI |
| 9003 | Jim | Brown | NY |
| 9004 | Jackie | Johnson | MI |
| 9005 | Joseph | Jackson | CA |
We are interested in customers that are located in Michigan and their first name starts with 'J'. So, the output would look like this:
Example Output:
| customer_id | first_name | last_name | state |
|---|---|---|---|
| 9001 | John | Smith | MI |
| 9002 | Jane | Doe | MI |
| 9004 | Jackie | Johnson | MI |
Answer:
Below is the PostgreSQL query you would use to answer this question:
Here’s the corrected version with the appropriate backticks:
This query will use the keyword to filter the table on the basis of the pattern 'J%' (which means any text that starts with J). In addition to this, we are also ensuring that the customer belongs to the state of Michigan using the state = 'MI' condition. The in the statement specifies that we want all the columns from the table that satisfy these conditions.
Preparing For The Stryker SQL Interview
The best way to prepare for a SQL interview, besides making sure you have strong SQL fundamentals, is to practice a ton of real SQL questions that were asked in recent job interviews. In addition to solving the above Stryker SQL interview questions, you should also solve the 200+ SQL questions on DataLemur which come from companies like FAANG (FB, Apple, Amazon, Netflix, Google).
Each SQL question has multiple hints, full answers and crucially, there's an online SQL code editor so you can instantly run your query and have it graded.
To prep for the Stryker SQL interview you can also be helpful to practice interview questions from other healthcare and pharmaceutical companies like:
- Viatris SQL questions
- Moderna SQL questions
- Tenet Healthcare SQL questions
- Becton Dickinson SQL questions
In case your SQL query skills are weak, don't worry about diving straight into solving questions – refresh your SQL knowledge with this DataLemur SQL tutorial.
This tutorial covers SQL topics like CASE/WHEN statements and turning a subquery into a CTE – both of which pop up routinely during Stryker interviews.
Stryker Data Science Interview Tips
What Do Stryker Data Science Interviews Cover?
In addition to SQL query questions, the other topics to practice for the Stryker Data Science Interview are:
- Experimental Design & AB Testing Questions
- Python or R Coding Questions
- Business Sense and Product-Sense Questions
- Machine Learning Questions
- Behavioral & Resume-Based Questions
How To Prepare for Stryker Data Science Interviews?
I think the best way to prepare for Stryker Data Science interviews is to read the book Ace the Data Science Interview.
It solves 201 data interview questions sourced from Facebook, Google, & Amazon. The book's also got a crash course covering SQL, Product-Sense & ML. And finally it's helped a TON of people, which is why it's earned 1000+ reviews on Amazon and a 4.5-star rating.
While the book is more technical in nature, it's also important to prepare for the Stryker behavioral interview. Start by reading the company's values and company principles.