10 BWX Technologies SQL Interview Questions (Updated 2024)

Updated on

December 7, 2023

At BWX Technologies, SQL is used across the company for analyzing nuclear operations data and for designing databases to securely store classified nuclear manufacturing secrets. That's why BWX Technologies LOVES to ask SQL problems during interviews for Data Analyst, Data Science, and BI jobs.

So, if you're trying to prepare for the SQL Assessment, here’s 10 BWX Technologies SQL interview questions to practice, which are similar to commonly asked questions at BWX Technologies – able to answer them all?

BWX Technologies

10 BWX Technologies SQL Interview Questions

SQL Question 1: Identify High-Value Customers for BWX Technologies

BWX Technologies is a supplier of nuclear components and fuel to the U.S. government. For the business, the most crucial activity is the high-frequency purchase or procurement of items. Here, we define a high-value customer as a customer who has placed orders more than a certain threshold in the recent 6-month period.

Use the following tables to identify the high-value customers.

Example Input:
Example Input:


Here's an SQL query to identify high-value customers:

This query first joins the and tables on the . Then, it filters out orders that were placed more than 6 months ago. It groups the remaining rows by and and counts the number of orders placed by each customer. Finally, it filters out customers who placed fewer than 10 orders over the past 6 months, leaving only the high-value customers.

To practice another SQL customer analytics question where you can solve it right in the browser and have your SQL solution instantly graded, try this Walmart Labs SQL Interview Question:

Walmart SQL Interview Question

SQL Question 2: Employee Analysis with Window Functions

BWX Technologies has a workforce divided into manufacturing and non-manufacturing employees across multiple locations.

Suppose there is a need to analyze each location's employee distribution, get the average salary for each department, and compare each individual's salary to their department average.

You are given a table :

Example Input:
101John DoeVirginiaManufacturing65000
102Jane SmithTennesseeNon-Manufacturing76000
103Mohamed AliTennesseeManufacturing72000
104Maria GarciaOhioManufacturing80000
105Paul WalkerVirginiaNon-Manufacturing85000

You need to write a SQL query that will provide information on each location, their department, the average department salary for that location, and how an employee's salary compares to the department average in their location.

Example Output:
VirginiaManufacturing65000John Doe65000100%
TennesseeManufacturing72000Mohamed Ali72000100%
OhioManufacturing80000Maria Garcia80000100%
VirginiaNon-Manufacturing85000Paul Walker85000100%
TennesseeNon-Manufacturing76000Jane Smith76000100%


In this query, a window function is used to calculate the average salary by each department at each location. This answer helps the HR department analyze their salary structure, and ensure employees are paid fairly across departments and locations, based on role expectations and market standards.

To practice a related window function SQL problem on DataLemur's free online SQL coding environment, solve this Google SQL Interview Question:

Google SQL Interview Question

SQL QUESTION 3: Can you explain the concept of database normalization?

Database normalization is the process of breaking down a table into smaller and more specific tables and defining relationships between them via foreign keys. This minimizes redundancy, and creates a database that's more flexible, scalable, and easier to maintain. It also helps to ensure the integrity of the data by minimizing the risk of data inconsistencies and anomalies.

SQL Question 4: Material and Supplier Management

BWX Technologies deals with many materials and suppliers to manufacture nuclear components. We are currently trying to optimize our database system to monitor the cost of materials and our interactions with suppliers more efficiently. For each material, we track its type, procurement cost and the supplier who provides it. As for the suppliers, we keep a log of their name, location and contact details.

Given this scenario, design a database structure that could handle this type of data and relationships among them effectively. Then, provide a SQL query to fetch all materials, their cost, and the details of the supplier, ordered by the cost of the materials in descending order.




1Supplier AUSAcontactA@mail.com
2Supplier BCanadacontactB@mail.com
3Supplier CUKcontactC@mail.com
4Supplier DRussiacontactD@mail.com


This SQL query will join the materials and suppliers table on the supplier_id field and select the required fields. The result will be sorted by the procurement_cost of materials in descending order. This way, it provides us with a detailed breakdown of each material, their cost, and the details of the supplier, allowing management to have comprehensive visibility over supply chain and cost management.

SQL QUESTION 5: What does the SQL keyword do?

The clause is used to remove all duplicate records from a query.

For example, if you had a table of open jobs BWX Technologies 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 6: Average Duration of Projects at BWX Technologies

BWX Technologies manages various projects throughout the year and they want to find the average duration of these projects in days. The duration of a project is calculated as the difference between the start date and end date.

Given the "projects" table, write an SQL query to calculate the average duration of the projects.

Table Example Input:

201Project Alpha01/01/202030/01/2020
202Project Beta15/01/202015/02/2020
203Project Gamma01/02/202028/02/2020
204Project Delta10/03/202030/03/2020

Expected Output:



This SQL query calculates the difference in days between the "end_date" and "start_date" for each row in the "projects" table using the DATEDIFF() function, then uses the AVG() function to calculate the average of these durations.

To practice a very similar question try this interactive Facebook Average Post Hiatus (Part 1) Question which is similar for calculating time duration between two events.

SQL QUESTION 7: What do foreign key's do?

A foreign key is a field in a database table that links to the primary key of another table, establishing a connection between the two tables.

To demonstrate this concept, let's analyze BWX Technologies's marketing analytics database which stores data from Google Ads campaigns:


+------------+------------+------------+------------+ | ad_id | campaign_id| keyword | click_count| +------------+------------+------------+------------+ | 1 | 100 | BWX Technologies pricing | 10 | | 2 | 100 | BWX Technologies reviews | 15 | | 3 | 101 | BWX Technologies alternatives | 7 | | 4 | 101 | buy BWX Technologies | 12 | +------------+------------+------------+------------+

is a foreign key. It references the of the Google Ads campaign that each ad belongs to, establishing a relationship between the ads and their campaigns. This foreign key allows you to easily query the table to find out which ads belong to a specific campaign, or to find out which campaigns a specific ad belongs to.

It is also possible for a table to have multiple foreign keys that reference different primary keys in other tables. For example, the table could have additional foreign keys for the of the ad group that each ad belongs to, and the of the Google Ads account that the campaigns belong to.

SQL Question 8: Analyze Click-Through-Rates for BWX Technologies

BWX Technologies use their website to market their products and services. They have a business need to optimize their online engagement. Specifically, they are interested in evaluating the click-through rate that results in a customer viewing a product to adding the product to the cart.

Using the tables and , calculate the click-through rate as the number of unique users who view a product and add it to the cart, divided by the total number of unique users who view the product.

Example Input:
501210107/01/2022 00:00:0090001
402310107/02/2022 00:00:0090001
800535507/01/2022 00:00:0090002
907667707/02/2022 00:00:0090001
108922207/03/2022 00:00:0090002
Example Input:
123410107/01/2022 00:00:0090001
567835507/01/2022 00:00:0090002
910167707/02/2022 00:00:0090001
112122207/03/2022 00:00:0090002
314122207/03/2022 00:00:0090001


This SQL query calculates the click-through rate for each product by:

  1. Joining the and tables based on the user_id and product_id.
  2. Counting the number of unique users who added the product to the cart, which is the numerator of the click-through rate.
  3. Dividing the above result by the number of unique users who viewed the product, which is the denominator of the click-through rate.
  4. Returning the rate for each product.

To solve a similar problem about calculating rates, solve this TikTok SQL Interview Question within DataLemur's interactive coding environment:

SQL interview question from TikTok

SQL Question 9: Locate Customer Records

BWX Technologies has a database of customer records which include a table named that store details about each purchase. You are to find records of all customers whose names start with the letter 'B' and reside in the state 'WA'.

Here's a snapshot of the table.

Example Input:
9281Brianna SmithWA1000110005/15/2022 00:00:00
4652Alex JohnsonCA200027504/20/2022 00:00:00
7219Bradley WilliamsWA1000215006/10/2022 00:00:00
8493Melinda JonesNY100035008/01/2022 00:00:00
1398Benjamin WatsonWA2000120007/18/2022 00:00:00

You are expected to produce a result that includes the , , , , and .


You can retrieve this data with the following SQL query:

This query uses the SQL keyword to match any records where the name column starts with 'B' and the state is 'WA'. The '%' sign is used as a wildcard to match any remaining characters after the 'B'.

Example Output:

9281Brianna SmithWA1000110005/15/2022 00:00:00
7219Bradley WilliamsWA1000215006/10/2022 00:00:00
1398Benjamin WatsonWA2000120007/18/2022 00:00:00

SQL QUESTION 10: Can you explain what SQL constraints are, and why they are useful?

Constraints are just rules your DBMS has to follow when updating/inserting/deleting data.

Say you had a table of BWX Technologies products and a table of BWX Technologies customers. Here's some example SQL constraints you'd use:

NOT NULL: This constraint could be used to ensure that certain columns in the product and customer tables, such as the product name and customer email address, cannot contain NULL values.

UNIQUE: This constraint could be used to ensure that the product IDs and customer IDs are unique. This would prevent duplicate entries in the respective tables.

PRIMARY KEY: This constraint could be used to combine the NOT NULL and UNIQUE constraints to create a primary key for each table. The product ID or customer ID could serve as the primary key.

FOREIGN KEY: This constraint could be used to establish relationships between the BWX Technologies product and customer tables. For example, you could use a foreign key to link the customer ID in the customer table to the customer ID in the product table to track which products each customer has purchased.

CHECK: This constraint could be used to ensure that certain data meets specific conditions. For example, you could use a CHECK constraint to ensure that BWX Technologies product prices are always positive numbers.

DEFAULT: This constraint could be used to specify default values for certain columns. For example, you could use a DEFAULT constraint to set the customer registration date to the current date if no value is provided when a new customer is added to the database.

How To Prepare for the BWX Technologies SQL Interview

The key to acing a BWX Technologies SQL interview is to practice, practice, and then practice some more! Beyond just solving the above BWX Technologies SQL interview questions, you should also solve the 200+ SQL Interview Questions on DataLemur which come from companies like Amazon, Microsoft, Meta, and smaller tech companies.

DataLemur Question Bank

Each problem on DataLemur has hints to guide you, step-by-step solutions and crucially, there's an online SQL code editor so you can right online code up your query and have it graded.

To prep for the BWX Technologies SQL interview it is also wise to practice SQL problems from other defense & aerospace contractors like:

However, if your SQL skills are weak, don't worry about going right into solving questions – strengthen your SQL foundations with this SQL tutorial for Data Scientists & Analysts.

DataLemur SQL Course

This tutorial covers things like finding NULLs and different types of joins – both of these come up routinely in SQL job interviews at BWX Technologies.

BWX Technologies Data Science Interview Tips

What Do BWX Technologies Data Science Interviews Cover?

For the BWX Technologies Data Science Interview, beyond writing SQL queries, the other types of questions to prepare for are:

  • Statistics and Probability Questions
  • Python or R Coding Questions
  • Data Case Study Questions
  • ML Modelling Questions
  • Behavioral Interview Questions

How To Prepare for BWX Technologies Data Science Interviews?

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

  • 201 interview questions sourced from companies like Google, Tesla, & Goldman Sachs
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