9 Moderna SQL Interview Questions (Updated 2024)

Data Analysts and Data Scientists at Moderna use SQL queries to analyze clinical trial datasets for vaccine efficiency, helping them assess how well their vaccines perform across different demographics. It is also used to manage data related to genomic research progress, ensuring that all findings are organized and easily retrievable for ongoing studies, this is the reason why Moderna frequently asks jobseekers SQL interview questions.

So, to help you prep for the Moderna SQL interview, we've curated 9 Moderna SQL interview questions in this blog.

9 Moderna SQL Interview Questions

SQL Question 1: Calculate the Monthly Average Vaccination Rate

As an analyst at Moderna, you have been provided with anonymized vaccination data. You are required to analyze the monthly trend of vaccinations. Specifically, you need to write a SQL query that calculates the average number of vaccinations administered per day for each month.

Example Input:

Example Output:

Answer:

This query uses the PostgreSQL function to get the month from the . It then calculates the average per day for each month using a window function with clause. Finally, it groups and orders the records by .

To practice a similar window function question on DataLemur's free interactive SQL code editor, try this Google SQL Interview Question:

Discover the exciting collaboration between Moderna and OpenAI as they work together to push the boundaries of mRNA medicine! This partnership highlights how innovative technologies are transforming healthcare, making it essential for you to understand the future of medical advancements.

SQL Question 2: Department vs. Company Salary

Assume there was a table of Moderna employee salary data, along with which department they belonged to. Write a query to compare the average salary of employees in each department to the company's average salary for March 2024. Return the comparison result as 'higher', 'lower', or 'same' for each department. Display the department ID, payment month (in MM-YYYY format), and the comparison.

Write a SQL query for this interview question and run your code right in DataLemur's online SQL environment:

The solution is LONG – 30+ lines of SQL. You can find a detailed solution here: Department vs. Company Salary.

SQL Question 3: When doing database schema design, what's an example of two entities that have a one-to-one relationship? What about one-to-many relationship?

In database schema design, a one-to-one relationship between two entities is where each entity is associated with only one instance of the other entity. For example, the relationship between a US citizen and their social-security number (SSN) is one-to-one, because each citizen can only have one SSN, and each SSN belongs to exactly one person.

On the other hand, a one-to-many relationship is where one entity can be associated with multiple instances of the 2nd entity. For example, each person can be associated with multiple email addresses, but each email address only relates back to one person.

SQL Question 4: Designing a Database for Moderna's Vaccine Distribution

Suppose you are a Data Engineer at Moderna, and you have been assigned to design a database system that will track the distribution of COVID-19 vaccines across different locations. Create the following tables: , , and , and model their relationships.

What columns would you include in these tables? How would you model the relationships between these tables?

Consider some important details such as the distribution date, the quantity of vaccines distributed, the type of vaccine, location details, and other aspects you consider vital for this situation.

Example Input:

Example Input:

Example Input:

Answer:

Here is an example PostgreSQL query to find the total quantity of each type of vaccine distributed in each city:

This PostgreSQL query will display a table with columns for , , and . The column will contain the sum of the quantity of vaccines distributed in each city, categorized by vaccine types. This information could be very beneficial for Moderna to keep track of their vaccine distribution and for future planning based on vaccine demand in locations.

SQL Question 5: In the context of a database transaction, what does ACID 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 Moderna store's it's data to be ACID-compliant!

SQL Question 6: Average Number of Vaccines Produced Per Day

As an analyst at Moderna, you're are asked to find the average number of vaccines produced per day given the production quantity and date.

Here is your task: Given a table that contains the , , , and , write a SQL query that calculates the for each .

Example Input:

Example Output:

Answer:

To solve this, we will use the AVG() function combined with GROUP BY:

This query groups the records by and computes the average for each group. We use the AVG() function here to calculate the average quantity per day, a key indicator of production efficiency and capacity.

To practice a very similar question try this interactive Amazon Average Review Ratings Question which is similar for average calculation or this Alibaba Compressed Mean Question which is similar for involving mean arithmetic operation.

SQL Question 7: What distinguishes an inner join from 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.

For a concrete example, imagine you had two database tables, an advertising campaigns table which had information on Google Ads keywords and how much was bid for each keyword, and a Moderna sales table, which has data on how many products were sold and which Google Ads keyword drove that sale.

: 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.

: 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 8: Analyzing Click-Through-Rates for Moderna's Vaccination Campaigns

Moderna is a biotech company that has been responsible for rolling out COVID-19 vaccines. Let's say the company runs a variety of digital ads prompting people to get vaccinated, and they are interested in understanding the Click-Through-Rates (CTR) of these ads. Further, they want to analyze the conversion rates from clicking on the ad to actually booking an appointment for vaccination.

Their data is stored across two tables:

Example Input:

Example Input:

We will be working with the and tables. Moderna would like to know:

1. The total number of clicks per ad ().
2. The total number of bookings per ad, only counting bookings that occurred after a click ().
3. The Click-Through-Rate (CTR = / ) for each ad.

The output should be formatted as follows: |ad_id|total_clicks|total_bookings|ctr|

Answer:

This SQL query joins the and tables on , and also ensures that the is after the . It then uses the clause to compute the total clicks, total bookings, and click-through rate for each ad. The click-through rate is calculated as the number of bookings divided by the number of ad clicks, converted to a decimal for accurate division.

To practice another question about calculating rates, try this TikTok SQL question within DataLemur's interactive coding environment:

SQL Question 9: Determine Most Used Vaccine

You are a data analyst working for Moderna, a biotech company famous for its COVID-19 vaccine. Moderna has two types of Covid vaccines, mRNA-1273 and mRNA-1273.351. The company has a vast database of patients and the vaccine they were administered.

One day, the head of the marketing department wants to understand the distribution of these vaccines in different age groups.

Write a SQL query that will display the number of patients in the following age groups - 'under 30', '30-45', '45-60' and 'over 60', who were administered either of the two vaccines.

Sample tables:

Table:

Table:

Answer:

This query calculates the age of the patient at the time of vaccine administration. It then groups the patients into specific age groups and counts the number of patients in each age group who received each type of vaccine. It finally orders the output by age group and vaccine type.

Because join questions come up frequently during SQL interviews, try an interactive Spotify JOIN SQL question:

Preparing For The Moderna 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 Moderna SQL interview questions, you should also solve the 200+ SQL Interview Questions on DataLemur which come from companies like Amazon, JP Morgan, and healthcare and pharmaceutical companies like Moderna.

Each interview question has hints to guide you, full answers and crucially, there is an online SQL coding environment so you can right in the browser run your SQL query and have it checked.

To prep for the Moderna SQL interview you can also be wise to solve SQL problems from other healthcare and pharmaceutical companies like:

• Tenet Healthcare SQL questions
• Becton Dickinson SQL questions
• Amgen SQL questions
• Gilead SQL questions

However, if your SQL coding skills are weak, forget about jumping right into solving questions – improve your SQL foundations with this DataLemur SQL Tutorial.

This tutorial covers SQL topics like handling NULLs in SQL and handling strings – both of which come up frequently during Moderna interviews.

Moderna Data Science Interview Tips

What Do Moderna Data Science Interviews Cover?

In addition to SQL query questions, the other types of questions tested in the Moderna Data Science Interview include:

• Stats Interview Questions
• Python or R Coding Questions
• Business Sense and Product-Sense Questions
• ML Interview Questions
• Behavioral Interview Questions based on Moderna values & principles

How To Prepare for Moderna Data Science Interviews?

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

• 201 interview questions taken from FAANG (FB, Apple, Amazon, Netflix, Google)
• a crash course on SQL, Product-Sense & ML
• over 1000+ 5-star reviews on Amazon

Don't ignore the behavioral interview – prep for that using this guide on acing behavioral interviews.