9 Nationwide SQL Interview Questions (Updated 2024)

Nationwide employees use SQL for analyzing and managing insurance claim data, including claim amounts and adjuster notes, as well as customizing customer experience based on policyholder behavior analysis by identifying high-risk customer segments. That is why Nationwide asks SQL problems in interviews for Data Science, Data Engineering and Data Analytics jobs.

Nationwide employees use SQL often for analyzing and managing insurance claim data, and customizing customer experience based on policyholder behavior analysis. That's why Nationwide typically asks SQL problems in interviews for Data Science, Data Engineering and Data Analytics jobs.

Thus, to help you prepare, here's 9 Nationwide SQL interview questions – able to answer them all?

9 Nationwide SQL Interview Questions

SQL Question 1: Identify Top Insurance Policyholders at Nationwide

Nationwide is a well-known insurance company. They would like to identify the customers who have purchased the most number of insurance policies in the last year. We are particularly interested in those customers who have purchased more than 5 different types of insurance policies. Your task is to find the user_id of these customers, the number of different insurance policies they've purchased, and the total amount they've spent.

We'll consider two tables and . The table records customer details, and each row in the table represents a particular insurance policy bought by a customer.

Example Input:

Example Input:

Answer:

This query pulls the user_id, the number of distinct policy types, and total amount they've spent from the table for purchases made in the last year. It then groups the result by user_id and only selects those users who have purchased more than 5 types of policies.

To practice a related customer analytics question on DataLemur's free online SQL coding environment, try this recently asked Microsoft SQL interview question:

SQL Question 2: Employees Earning More Than Their Boss

Suppose you had a table of Nationwide employee salaries. Write a SQL query to find the employees who earn more than their direct manager.

Nationwide Example Input:

Example Output:

This is the output because Olivia Smith earns $8,000, surpassing her manager, William Davis who earns 7,800.

Test your SQL query for this interview question 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 solution above is tough, you can find a step-by-step solution with hints here: Employee Salaries Higher Than Their Manager.

SQL Question 3: What's a database view, and what's it used for?

A database view is a virtual table that is created based on the results of a SELECT statement, and provides you a customized, read-only version of your data that you can query just like a regular table.

You'd want to use a view for a few reasons:

• views allow you to create a simpler versions of your data based on whose running the query (such as hiding un-important columns/rows from business analysts if they're just random noisy artifricats of your Data Infrastructure pipelines)
• views can help you comply with information security requirements by hiding sensitive data from certain users (important for regulated industries like govermnet and healthcare!)
• views often improve performance for complicated queries by pre-computing the results and saving them in a view (which is often faster than re-executing the original query)... just be careful since static views don't update if the underlying data changes!

SQL Question 4: Average Premium Per Product By Month

Assume that Nationwide is interested in monitoring the performance of their financial products. Each user pays a monthly insurance premium for a particular product. You're asked to write a SQL query that will calculate the average premium by product and month over the year of 2022.

We'll work with a table which has the following structure:

Example Input:

We want to generate a report with columns "month", "product" and "average_premium".

Example Output:

Answer:

Here's the PostgreSQL query that can be used to answer this question:

This query first filters out records from 2022. It then groups the remaining records by the payment month (extracted from payment_date) and product_id, while calculating the average premium in each group. Finally, it orders the results by month and product.

To solve a similar window function interview problem which uses RANK() on DataLemur's free online SQL coding environment, solve this Amazon BI Engineer interview question:

SQL Question 5: What does the keyword do?

If you want to return records with no duplicates, you can use the keyword in your statement.

For example, if you had a table of Nationwide employees, and wanted to see what are all the unique job titles that currently worked at the company, you could write the following query:

If had the following data:

Then the output from the query would be:

SQL Question 6: Filtering Nationwide Customers Data

Given a list of Nationwide's customers, write a SQL query to extract customers living in Ohio state, with an active account status, their age is above 21, and they have a home loan either with a fixed or adjustable rate.

Please note that the given tables don't include every single attribute you might find in Nationwide's actual customer databases, but it includes the necessary fields for this problem:

Example Input:

Example Input:

The output of your SQL query should include the , , , and .

Answer:

This SQL query first performs an inner join between the table and the table based on the . Then it uses a WHERE clause to filter out the customers based on the conditions described in the question - customers living in Ohio with active accounts, aged over 21, with either a fixed or adjustable rate home loan. The SELECT clause only extracts the necessary fields for the output.

SQL Question 7: Could you explain what a self-join is and provide examples of when it might be used?

A self-join is a type of join in which a table is joined to itself. To perform a self-join, you need to specify the table name twice in the clause, and give each instance of the table a different alias. You can then join the two instances of the table using a clause, and use a clause to specify the relationship between the rows.

For example, say you were doing an HR analytics project and needed to analyze how much all Nationwide employees in the same department interact with each other. Here's a self-join query you could use to retrieve all pairs of Nationwide employees who work in the same department:

This query returns all pairs of Nationwide employees who work in the same department, and excludes pairs where the employee's id is the same (since this would represent the same Nationwide employee being paired with themselves).

SQL Question 8: Average Number of Claims Per Policy on Nationwide

Nationwide is an insurance company, so you could answer something pertaining to insurance claims. For example, you may need to find the average number of claims per insurance policy.

We'll need two tables for this problem. The first is , which represents all active insurance policies, and the second is , which represents all claims made against those policies.

Example Input:

Example Input:

We want to find out the average number of claims per policy.

Answer:

This query joins the table with the table on the field. It then groups the result by and calculates the average of the and count number of claims for each . If a policy does not have associated claim, then it will not be included in the output. If all policies should be included regardless of whether they have associated claims or not, a LEFT JOIN should be used instead.

To practice a very similar question try this interactive CVS Health Pharmacy Analytics (Part 1) Question which is similar for analyzing key metrics based on transactions or this Stripe Repeated Payments Question which is similar for identifying duplicated transactions.

SQL Question 9: Calculate the average insurance claim amount for each insurance type

Nationwide is a large insurance company. Therefore, they may be interested in understanding the average claim amount for each insurance type.

Suppose the company maintains a table named with the following schema:

Example Input:

In this scenario, we would like to know the average claim amount for each insurance type.

Answer:

You can accomplish this through the following SQL query:

In this query, we are using the clause to group the records by their and then calculating the average of for each group.

Example Output:

The query gives the desired output where we can see the average claim amount for 'auto' is 5000, for 'home' is 12500, and for 'pet' is 750.

Preparing For The Nationwide SQL Interview

The best way to prepare for a Nationwide SQL interview is to practice, practice, practice. Beyond just solving the earlier Nationwide SQL interview questions, you should also solve the 200+ FAANG SQL Questions on DataLemur which come from companies like Amazon, JP Morgan, and insurance companies like Nationwide.

Each SQL question has hints to guide you, step-by-step solutions and crucially, there is an interactive SQL code editor so you can easily right in the browser your SQL query answer and have it checked.

To prep for the Nationwide SQL interview it is also wise to solve interview questions from other insurance companies like:

• Progressive SQL questions
• Liberty Mutual SQL questions
• New York Life SQL questions
• AIG SQL questions

Stay ahead of the curve with Nationwide's latest announcements and updates!

However, if your SQL query skills are weak, forget about diving straight into solving questions – improve your SQL foundations with this DataLemur SQL Tutorial.

This tutorial covers SQL topics like aggregate window functions and filtering data with boolean operators – both of which pop up frequently during Nationwide SQL assessments.

Nationwide Data Science Interview Tips

What Do Nationwide Data Science Interviews Cover?

In addition to SQL interview questions, the other types of questions covered in the Nationwide Data Science Interview are:

• Probability & Statistics Questions
• Python or R Coding Questions
• Data Case Study Questions
• ML Modelling Questions
• Behavioral & Resume-Based Questions

How To Prepare for Nationwide Data Science Interviews?

To prepare for the Nationwide Data Science interview make sure you have a deep understanding of the company's values and mission – this will be important for acing the behavioral interview. For technical interviews prepare by reading Ace the Data Science Interview. The book's got:

• 201 Interview Questions from Microsoft, Amazon & startups
• A Refresher on SQL, AB Testing & ML
• Amazing Reviews (1000+ 5-star reviews on Amazon)