11 Biogen SQL Interview Questions (Updated 2024)

Biogen employees write SQL queries for analyzing complex genomic data, which allows them to uncover insights that drive innovative treatments for neurological diseases. They also manage clinical trial data efficiently, ensuring that all information is accurate and reliable, which is crucial for maintaining data integrity in the biotechnology industry. For this reason, Biogen tests SQL coding questions during interviews for Data Analytics, Data Science, and Data Engineering jobs.

Thus, to help you prep, here’s 11 Biogen SQL interview questions – able to answer them all?

11 Biogen SQL Interview Questions

SQL Question 1: Calculate Monthly Drug Usage

Biogen is a biotechnology company that develops drugs for health conditions. In this example, let's assume that we are tracking the usage of various drugs among patients every month. We are primarily interested in the total quantity of each drug used per month. To investigate this, we need to write a SQL query that will calculate the total monthly usage for each drug.

For this question, suppose we have the following table, represented as follows:

Example Input:

This table has columns for (unique identifier for a drug usage event), (identifying the patient who used the drug), (the date on which the drug was used), (the identifier for the drug used), and (the amount of the drug used).

We want to produce a result that, for each month and each drug, shows the total quantity used. The result table should look like this:

Example Output:

To solve this problem, we can extract the month from the field and group by this and the to get the total quantity used for each drug per month.

Answer:

The following SQL query should give us the desired output:

This PostgreSQL SQL query first extracts the month part of the using the function. It then leverages the SQL window function , which calculates the sum of for each partition of data. The keyword divides the table into partitions based on the month and . Finally, it sorts the result by month and drug.

To solve another window function question on DataLemur's free interactive coding environment, solve this Google SQL Interview Question:

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SQL Question 2: Top 3 Department Salaries

Imagine there was a table of Biogen employee salary data. Write a SQL query to find the top three highest paid employees in each department.

Biogen Example Input:

Example Input:

Example Output:

Solve this interview question interactively on DataLemur:

Answer:

We use the DENSE_RANK() window function to generate unique ranks for each employee's salary within their department, with higher salaries receiving lower ranks. Then, we wrap this up in a CTE and filter the employees with a ranking of 3 or lower.

If the solution above is hard to understand, you can find a step-by-step solution with hints here: Top 3 Department Salaries.

SQL Question 3: 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 Biogen working on a Marketing Analytics project. If you needed to get the combined result set of both Biogen'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 4: Drug Inventory Management

Biogen, a globally renowned biotechnology company, develops and produces treatments for neurodegenerative, hematologic, and autoimmune diseases. One primary concern for them is to ensure their drug inventory is managed efficiently, to fulfill the demands on time and prevent drug expiry.

Your job is to design a database capturing information about drugs, their production batches, and inventory across multiple warehouses. Additionally, Biogen wants to track the total quantity of each drug available in all warehouses.

Example Input:

Example Input:

Example Input:

Can you write a SQL query to retrieve the total quantity of each drug available in all warehouses, along with the drug name?

Answer:

The following query would suffice:

This PostgreSQL query joins the table with the table based on the common column . It then computes the total quantity for each drug across all the warehouses using the function and groups the results by drug name.

SQL Question 5: Can you explain what SQL constraints are, and why they are useful?

SQL constraints are used to specify rules for the data in a table. They can be applied to single or multiple fields in a table when the table is created, or after the table has been created using the ALTER TABLE command.

For example, say you had a database that stores ad campaign data from Biogen's Google Analytics account.

Here's what some constraints could look like:

SQL Question 6: Filter Customers Based on Multiple Criteria

Given a database of Biogen's customers, your task is to write a SQL query to filter customers based on three conditions. The conditions are as follows:

1. The customer's age is greater than or equal to 50.
2. The customer is a male.
3. The customer has purchased Alzheimer medication.

Assume the database has a table named with the following structure:

Example Input:

The output should return the , and of the customers who meet the criteria.

Example Output:

Answer:

The following SQL command can solve this task:

This query filters the customer records using clause with three conditions separated by operators which check the age, gender and if the customer purchased Alzheimer medication. The query then returns the , , and of the customers that satisfy all the conditions.

SQL Question 7: When would you use denormalization?

Denormalization is the practice of altering a database schema in a way that breaks the normalization rules (1st, 2nd, 3rd normal forms).

For example, in a database that stores Biogen sales analytics data, you might have separate tables for "customers," "orders," and "products," with foreign key constraints linking the tables together. This helps to ensure the integrity of the data and reduces redundancy, but it can also make queries that involve multiple tables more complex and slower to execute.

By de-normalizing the database, you can combine some of the data from separate tables into a single table, which can reduce the number of joins that are required to retrieve the data you need. This can speed up queries and improve the performance of your database.

However, it's important to carefully consider the trade-offs of de-normalization before making any changes to your database. De-normalization can make it more difficult to maintain the integrity and reliability of your data, and can also increase the risk of data redundancy. It's generally best to use de-normalization as a performance optimization technique only when necessary, and to carefully evaluate the benefits and drawbacks in the context of your specific database and workload.

SQL Question 8: Average Research Expense on Projects

In the biotech industry, companies like Biogen constantly have multiple research projects underway, each with their distinct set of expenses. You are to determine the average cost per research project done by Biogen.

Example Input:

Example Input:

Example Output:

Answer:

This query first groups the expense data by and then applies the function to calculate the average expense () for each research project. This provides an overview of how much Biogen has spent on average for each of its research projects.

To practice a very similar question try this interactive Amazon Highest-Grossing Items Question which is similar for calculating top items in categories or this CVS Health Pharmacy Analytics (Part 1) Question which is similar for identifying top profitable items.

SQL Question 9: Average Monthly Sales of Each Drug

As a data analyst at Biogen, your task is to calculate the average monthly sales for each drug for the year 2021.

Example Input:

Example Output:

Answer:

This query begins by selecting the month from the , the , and the average quantity sold for each drug.

It then specifies that the data is pulled from the table, filtering to include only sales from the year 2021.

The results are then grouped by both the extracted and the , aggregating the data for each row.

Finally, the query orders the results by month and by the average quantity in descending order, allowing for easy identification of which drug had the highest average sales each month.

SQL Question 10: When would you use the function?

The function allows you to select the first non-NULL value from a list of values. It is often used to replace a NULL value with a default value in order to run aggregate functions like or on a column without being affected by values.

For example, if you conducted a customer satisfaction survey for a company and asked customers to rate their level of agreement with a statement on a scale of 1 to 10, some customers may not have answered all the questions, resulting in NULL values in the survey data:

To replace the NULLs in the column with the default value of 5 which corresponds to neutral on the survey, you could run the following SQL query:

You'd get the following output:

SQL Question 11: Join Customer and Orders Tables

As the new data analyst at Biogen, your manager asks you to analyze the customer and orders data. Write a SQL query that retrieves all the customers who have made purchases in 2022 together with the total amounts for those purchases. Note that you should only consider those customers who have made at least one purchase.

Here's the necessary input data for the problem:

Example Input:

Example Input:

Answer:

You can achieve this by using a combination of and . Here's a suitable query:

This query first connects the table with the table using the field, which is common to both tables. After that, it filters out the orders that have been made in 2022 and finally groups the result by . The clause is used to only include customers who have made at least one purchase.

Because join questions come up so often during SQL interviews, practice an interactive Spotify JOIN SQL question:

How To Prepare for the Biogen 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 earlier Biogen SQL interview questions, you should also solve the 200+ SQL questions from real Data Science & Analytics interviews which come from companies like Google, Microsoft and Silicon Valley startups.

Each SQL question has hints to guide you, detailed solutions and most importantly, there's an online SQL code editor so you can instantly run your SQL query answer and have it graded.

To prep for the Biogen SQL interview you can also be useful to solve SQL questions from other healthcare and pharmaceutical companies like:

• Gilead SQL questions
• Boston Scientific SQL questions
• Amgen SQL questions
• Henry Schein SQL questions

But if your SQL coding skills are weak, forget about diving straight into solving questions – strengthen your SQL foundations with this free SQL for Data Analytics course.

This tutorial covers SQL concepts such as LEAD/LAG window functions and UNION – both of these come up often in SQL job interviews at Biogen.

Biogen Data Science Interview Tips

What Do Biogen Data Science Interviews Cover?

Besides SQL interview questions, the other question categories covered in the Biogen Data Science Interview include:

• Statistics and Probability Questions
• Python Pandas or R Coding Questions
• Product Analytics Questions
• Machine Learning Questions
• Behavioral Interview Questions centered on Biogen company values

How To Prepare for Biogen Data Science Interviews?

To prepare for Biogen Data Science interviews read the book Ace the Data Science Interview because it's got:

• 201 interview questions sourced from FAANG, tech startups, and Wall Street
• a crash course on Stats, SQL & ML
• over 1000+ 5-star reviews on Amazon

Also focus on the behavioral interview – prep for it using this guide on behavioral interview questions.