6 Northrop Grumman SQL Interview Questions (Updated 2024)
At Northrop Grumman, SQL does the heavy lifting for querying vast military intelligence databases to extract insights, and for analyzing supply-chain data related to the missiles, ships, and drones they make. Because of this, Northrop Grumman frequently asks SQL problems during interviews for Data Analyst, Data Science, and BI jobs.
So, if you're preparing for a SQL Interview, here’s 6 Northrop Grumman SQL interview questions to practice, which are similar to commonly asked questions at Northrop Grumman – can you solve them?
Northrop Grumman SQL Interview Questions
SQL Question 1: Identify the Power Users of Northrop Grumman
Building mission critical systems for the government is no easy task. That's why Northrop Grumman has a large database of project interactions recorded on their internal task management system. A "project interaction" refers to any task creation, completion, or action performed on an existing project. The tasks could be of various types like design, development, testing, documentation, maintenance and so forth. They want to identify their power users, who are users who have performed the maximum number of project interactions in the past month.
The structure of their table is as follows:
Sample Input:
| interaction_id | user_id | project_id | interaction_date | interaction_type |
|---|---|---|---|---|
| 101 | 7 | 401 | 06/08/2022 | Design |
| 102 | 5 | 334 | 06/10/2022 | Testing |
| 103 | 3 | 401 | 06/10/2022 | Development |
| 104 | 2 | 334 | 06/18/2022 | Maintenance |
| 105 | 4 | 401 | 07/05/2022 | Documentation |
| 106 | 7 | 334 | 07/06/2022 | Design |
| 107 | 3 | 334 | 07/26/2022 | Development |
Given the above table, write a SQL query to extract the top 3 users who had the most interactions in the month of June.
Answer:
This query groups all interactions by that occurred in the month of June, counts the interactions, and orders them in descending order by the interaction count. The LIMIT keyword restricts the output to the top 3 users.
To practice another similar SQL question where you can solve it interactively and have your SQL code instantly executed, try this Walmart Labs SQL Interview Question:
SQL Question 2: Employee Performance Analysis
Northrop Grumman wants to measure its employee performance on an ongoing basis. The Human Resources Department has compiled a dataset with all projects completed by the employees and the time taken to complete them.
Example Input:
| employee_id | project_id | completion_date | hours_spent |
|---|---|---|---|
| 1001 | 7001 | 01/02/2022 | 45 |
| 1002 | 7002 | 01/16/2022 | 55 |
| 1001 | 7003 | 02/07/2022 | 50 |
| 1002 | 7004 | 02/14/2022 | 65 |
| 1003 | 7005 | 02/20/2022 | 40 |
Now the HR wants to find out for each employee, the average number of hours they have spent per month. They are particularly interested in the months and employees where the monthly average is greater than 50.
Write a SQL query that performs this analysis.
Expected Output:
| month | employee | avg_hours |
|---|---|---|
| 1 | 1002 | 55.00 |
| 2 | 1001 | 50.00 |
| 2 | 1002 | 65.00 |
Answer:
This SQL query first extracts the month from the completion_date column and then groups by the month and employee_id. The average number of hours spent on projects is then calculated for each group. Finally, rows are only selected if the average number of hours is greater than 50. By using a window function, the company can efficiently analyze the performance of its employees across different months.
p.s. Window functions show up super often during SQL interviews, so practice the 27+ window function questions on DataLemur
SQL QUESTION 3: Can you provide an example of two entities that have a one-to-one relationship, and another example of a one-to-many relationship?
In database schema design, a one-to-one relationship is when each entity is associated with only one instance of the other. For instance, a US citizen's relationship with their social-security number (SSN) is one-to-one because each citizen can only have one SSN, and each SSN belongs to one person.
A one-to-many relationship, on the other hand, is when one entity can be associated with multiple instances of the other entity. An example of this is the relationship between a person and their email addresses - one person can have multiple email addresses, but each email address only belongs to one person.
p.s. Window functions show up super often during SQL interviews, so practice the 27+ window function questions on DataLemur
SQL Question 4: Average Number of Projects Handled Per Engineer at Northrop Grumman
At Northrop Grumman, a pertinent question could be to find the average number of projects handled by an engineer. This could help analyze workload distribution and resource management.
Example Input:
| engineer_id | first_name | last_name |
|---|---|---|
| 103 | Jane | Doe |
| 365 | John | Smith |
| 798 | Mary | Jones |
Example Input:
| project_id | engineer_id | project_name | start_date | end_date |
|---|---|---|---|---|
| 90001 | 103 | Alpha | 01/01/2023 | 12/31/2023 |
| 90002 | 365 | Bravo | 01/02/2023 | 12/31/2023 |
| 90003 | 365 | Charlie | 02/01/2023 | 12/31/2023 |
| 90004 | 798 | Delta | 03/01/2023 | 12/31/2023 |
| 90005 | 798 | Echo | 05/01/2023 | 12/31/2023 |
Answer:
This query first creates a subquery that counts how many projects each engineer is assigned. It then joins this subquery with the Engineers table and calculates the average number of projects for each engineer.
To practice a very similar question try this interactive Twitter Histogram of Tweets Question which is similar for calculating aggregates per unique entity or this Uber User's Third Transaction Question which is similar for analyzing frequency of associated events.
SQL QUESTION 5: Could you describe the function of UNION in SQL?
The operator merges the output of two or more statements into a single result set. The two SELECT statements within the UNION must have the same number of columns and the data types of the columns are all compatible.
For example, if you were a Data Analyst on the marketing analytics team at Northrop Grumman, this statement would return a combined result set of both Northrop Grumman's Google and Facebook ads that have more than 300 impressions:
SQL QUESTION 6: How do the 'BETWEEN' and 'IN' commands differ?
is used to select rows that match a range of values, whereas the operator checks for values in a specified list of values.
For example, say you were a Data Analyst at Northrop Grumman and had a table of advertising campaign data.
To find campaigns with between 10k in spend, you could use BETWEEN`:
To find ad campaigns that were run on Facebook and Google's Display Network, you could use :
I'm sorry, but you haven't provided a SQL question to solve. Could you please provide a SQL question so that I can generate the required Sample tables and SQL query?
Northrop Grumman SQL Interview Tips
Assuming that you've already got basic SQL skills, the next best tip we have to prepare for the Northrop Grumman SQL interview is to solve as many practice SQL interview questions as you can! In addition to solving the earlier Northrop Grumman SQL interview questions, you should also solve the 200+ SQL questions on DataLemur which come from companies like Facebook, Google, and VC-backed startups.
Each interview question has hints to guide you, detailed solutions and crucially, there's an interactive coding environment so you can easily right in the browser your SQL query and have it executed.
To prep for the Northrop Grumman SQL interview it is also useful to solve interview questions from other defense & aerospace contractors like:
But if your SQL coding skills are weak, forget about going right into solving questions – refresh your SQL knowledge with this DataLemur SQL tutorial.
This tutorial covers things like handling dates and rank window functions – both of which show up often during Northrop Grumman interviews.
Northrop Grumman Data Science Interview Tips
What Do Northrop Grumman Data Science Interviews Cover?
For the Northrop Grumman Data Science Interview, beyond writing SQL queries, the other types of questions to prepare for are:
- Probability & Statistics Questions
- Python or R Programming Questions
- Data Case Study Questions
- Machine Learning and Predictive Modeling Questions
- Behavioral Interview Questions
How To Prepare for Northrop Grumman Data Science Interviews
To prepare for Northrop Grumman Data Science interviews read the book Ace the Data Science Interview because it's got:
- 201 interview questions sourced from Facebook, Google & startups
- a refresher on SQL, Product-Sense & ML
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