11 United Natural Foods SQL Interview Questions (Updated 2024)
At United Natural Foods, SQL is used to analyze sales trends across various natural food categories, helping them identify which products are becoming popular. They also use SQL to improve distribution routes based on detailed purchase data to ensure that deliveries are efficient and timely, which is why United Natural Foods often asks SQL questions during interviews for Data Analyst, Data Science, and BI jobs.
So, to help you practice, we've collected 11 United Natural Foods SQL interview questions – how many can you solve?
11 United Natural Foods SQL Interview Questions
SQL Question 1: Find the Monthly Total Quantity and Average Cost of Each Product
United Natural Foods is a distributor of natural and organic foods in the United States and Canada. The company operates through three segments: Wholesale, Retail, and Manufacturing and Branded Products.
Assume that United Natural Foods has a monthly records table that keeps track of each product's quantity and cost. Write a SQL query that will compute the total quantity and average cost for each product per month in 2022, taking advantage of window functions.
Here's the sample data:
Example Input:
| record_id | product_id | record_date | quantity | cost |
|---|---|---|---|---|
| 1 | 1001 | 01/01/2022 | 500 | 5.00 |
| 2 | 1002 | 01/15/2022 | 300 | 7.00 |
| 3 | 1001 | 02/01/2022 | 600 | 4.50 |
| 4 | 1002 | 02/19/2022 | 200 | 7.50 |
| 5 | 1001 | 03/01/2022 | 700 | 4.75 |
We want to produce an output that summarizes the amount of each product supplied and the average cost per month:
Example Output:
| month | product_id | total_quantity | avg_cost |
|---|---|---|---|
| 1 | 1001 | 500 | 5.00 |
| 1 | 1002 | 300 | 7.00 |
| 2 | 1001 | 600 | 4.50 |
| 2 | 1002 | 200 | 7.50 |
| 3 | 1001 | 700 | 4.75 |
Answer:
This query uses the clause to apply the and functions to each subset of rows, partitioned by and month. The function is used to get the month and year from the . The clause restricts the results to the year 2022. The results are then ordered by and .
p.s. Window functions show up pretty frequently during SQL interviews, so practice the 27+ window function questions on DataLemur
Discover United Natural Foods' news and resources to learn about their commitment to sustainability and innovation in the food industry! By following UNFI's journey, you can gain insights into how companies are responding to consumer demands and industry challenges.
SQL Question 2: Employees Earning More Than Managers
Imagine you had a table of United Natural Foods employee salary data. Write a SQL query to find all employees who earn more than their direct manager.
United Natural Foods Example Input:
| employee_id | name | salary | department_id | manager_id |
|---|---|---|---|---|
| 1 | Emma Thompson | 3800 | 1 | |
| 2 | Daniel Rodriguez | 2230 | 1 | 10 |
| 3 | Olivia Smith | 8000 | 1 | 8 |
| 4 | Noah Johnson | 6800 | 2 | 8 |
| 5 | Sophia Martinez | 1750 | 1 | 10 |
| 8 | William Davis | 7000 | 2 | NULL |
| 10 | James Anderson | 4000 | 1 | NULL |
Example Output:
| employee_id | employee_name |
|---|---|
| 3 | Olivia Smith |
This is the output because Olivia Smith earns $8,000, surpassing her manager, William Davis who earns 7,800.
Check your SQL query for this interview question and run your code right in DataLemur's online SQL environment:
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 confusing, you can find a step-by-step solution here: Employee Salaries Higher Than Their Manager.
SQL Question 3: What are some ways you can identify duplicates in a table?
One creative way is to use the window function and partition by whichever columns you are looking for duplicates in. If any row has a row_number() greater than 1, then it's a duplicate!
You could also use vs. and see if they return different numbers, indicating the presence of duplicates!
SQL Question 4: Analyzing product sales patterns
United Natural Foods is interested in finding out the total sales amount and quantity of each product for every month, to better understand their sales patterns. You are given two tables - and .
The table has the following fields:
- : the unique identifier of an order.
- : the identifier of the product bought in this order.
- : the number of units of the product bought in this order.
- : the total price of the units bought in this order.
- : the date when the order was placed.
The table has the following fields:
- : the unique identifier of a product.
- : the name of the product.
Design a SQL query that gives the total sales quantity and total sales amount of each product for each month.
Example Input:
| order_id | product_id | quantity | total_price | order_date |
|---|---|---|---|---|
| 9156 | 3001 | 2 | 20 | 2022-01-15 |
| 3762 | 5002 | 1 | 15 | 2022-01-20 |
| 6483 | 6001 | 3 | 45 | 2022-02-10 |
| 4956 | 3001 | 4 | 40 | 2022-02-22 |
Example Input:
| product_id | product_name |
|---|---|
| 3001 | Organic Apples |
| 5002 | Gluten-Free Bread |
| 6001 | Raw Almonds |
Answer:
The PostgreSQL query to solve the problem is as follows:
In the query above, gets the month and year of each order. Then for each month and each product, the quantity and total_price are summed up using the and respectively. The JOIN operation links the product info from the table with the sales data in . The result is grouped by and . It is ordered by and to get chronologically ordered sales data for each product.
SQL Question 5: What's the difference between a left and right join?
A join in SQL combines rows from two or more tables based on a shared column or set of columns. To demonstrate the difference between a and , say you had a table of United Natural Foods orders and United Natural Foods customers.
LEFT JOIN: A retrieves all rows from the left table (in this case, the Orders table) and any matching rows from the right table (the Customers table). If there is no match in the right table, NULL values will be returned for the right table's columns.
RIGHT JOIN: A retrieves all rows from the right table (in this case, the Customers table) and any matching rows from the left table (the Orders table). If there is no match in the left table, NULL values will be returned for the left table's columns.
SQL Question 6: Filter Customer Records for Promotional Campaign
United Natural Foods is launching a new promotional campaign. To select customers who are eligible for this promotion, they have set some requirements on their food purchasing records. The requirements are:
- The total spend on organic foods in the past 6 months must be greater than $500.
- The customer has purchased at least 5 different types of vegetables in the last 3 months.
- The customer has not bought any products from the 'Dairy' category in the last month.
Given a table and a table, write a query that will select the , , and of all customers who meet these requirements.
Example Input:
| customer_id | first_name | last_name |
|---|---|---|
| 1134 | Jane | Doe |
| 2358 | John | Smith |
| 3632 | Emily | Johnson |
| 4856 | Robert | Brown |
Example Input:
| purchase_id | customer_id | product_category | product_type | amount_spent | purchase_date |
|---|---|---|---|---|---|
| 5012 | 1134 | Organic | Tomatoes | 60 | 2022-06-12 |
| 6578 | 1134 | Organic | Broccoli | 50 | 2022-06-18 |
| 7890 | 1134 | Organic | Potatoes | 80 | 2022-07-03 |
| 5432 | 1134 | Dairy | Milk | 100 | 2022-07-10 |
| 5326 | 2358 | Organic | Carrots | 260 | 2022-06-15 |
| 8765 | 2358 | Organic | Onions | 80 | 2022-06-20 |
| 3245 | 2358 | Organic | Garlic | 90 | 2022-07-08 |
| 2546 | 2358 | Organic | Potatoes | 100 | 2022-08-02 |
| 5678 | 2358 | Dairy | Yogurt | 70 | 2022-05-15 |
Answer:
In this query, we first filter out customers who have spent more than $500 on organic foods in the past 6 months. Then out of these, we further filter out customers who have purchased at least 5 different types of vegetables in the last 3 months. Finally, we exclude customers who have bought dairy products in the past month.
SQL Question 7: Can you explain the concept of a constraint in SQL?
Constraints are used to specify the rules concerning data in the table. It can be applied for single or multiple fields in an SQL table during the creation of the table or after creating using the ALTER TABLE command. The constraints are:
Say you were storing sales analytics data from United Natural Foods's CRM inside a database. Here's some example constraints you could use:
-
PRIMARY KEY constraint: You might use a constraint to ensure that each record in the database has a unique identifier. For example, you could use the field as the primary key in the table.
-
FOREIGN KEY constraint: You might use a constraint to link the data in one table to the data in another table. For example, you could use a foreign key field in the table to reference the field in the table.
-
NOT NULL constraint: You might use a constraint to ensure that a field cannot contain a value. For example, you could use a constraint on the field in the table to ensure that each opportunity has a name.
-
UNIQUE constraint: You might use a constraint to ensure that the data in a field is unique across the entire table. For example, you could use a constraint on the field in the table to ensure that each contact has a unique email address.
-
CHECK constraint: You might use a constraint to ensure that the data in a field meets certain conditions. For example, you could use a constraint to ensure that the field in the table is a value between 0 and 100.
-
DEFAULT constraint: You might use a constraint to specify a default value for a field. For example, you could use a constraint on the field in the table to set the default value to .
SQL Question 8: Analyzing Click-Through Rates for United Natural Foods
United Natural Foods Inc. (UNFI) has been using digital advertising to promote organic foods across various platforms. The marketing team wants to understand the click-through rates of these digital ads to optimize its campaigns. For an ad campaign, a 'click-through' is recorded when a user clicks on the ad and a 'conversion' is counted when the same user adds a product to the cart after clicking the ad. Your task is to help the marketing team by calculating the click-through conversion rates for each product in the last month.
To assist you in this task, you have the two tables outlined below
Example Input:
| click_id | user_id | click_date | product_id |
|---|---|---|---|
| 101 | 324 | 06/30/2022 | 50056 |
| 202 | 111 | 07/01/2022 | 50059 |
| 303 | 489 | 06/25/2022 | 50056 |
| 404 | 245 | 06/30/2022 | 50059 |
| 505 | 111 | 07/02/2022 | 50058 |
Example Input:
| conversion_id | user_id | conversion_date | product_id | quantity |
|---|---|---|---|---|
| 5001 | 324 | 06/30/2022 | 50056 | 3 |
| 6002 | 245 | 06/30/2022 | 50059 | 2 |
| 7003 | 324 | 06/30/2022 | 50056 | 1 |
| 8004 | 245 | 06/30/2022 | 50059 | 2 |
| 9005 | 489 | 06/30/2022 | 50056 | 1 |
Answer:
This query will return the click-through conversion rate for each product in the last month. The conversion rate is calculated as the number of conversions divided by the number of clicks, multiplied by 100 to obtain a percentage. The products are then ordered in decreasing order of their conversion rates.
To solve a similar problem about calculating rates, try this TikTok SQL question within DataLemur's online SQL code editor:
SQL Question 9: Find customer records from the west coast region
As an SQL engineer at United Natural Foods, your job is to occasionally perform data analysis to ensure customer information is kept up-to-date and useful. You're requested to retrieve customer records that are from three specific states related to the company's west coast operations - California, Oregon, and Washington. The customer records must match the pattern of these three states.
Example Input:
| customer_id | first_name | last_name | address | state | |
|---|---|---|---|---|---|
| 5171 | John | Doe | 123 Main St, Los Angeles | johndoe@email.com | California |
| 7802 | Sarah | Smith | 456 Pine St, Portland | sarahsmith@email.com | Oregon |
| 5293 | Alex | Harris | 789 Oak St, Seattle | alexharris@email.com | Washington |
| 6352 | Julie | Brown | 321 Elm St, Phoenix | juliebrown@email.com | Arizona |
| 4517 | Mike | Davis | 654 Maple St, Austin | mikedavis@email.com | Texas |
Answer:
This PostgreSQL command utilizes the SQL keyword LIKE to filter customer records by state. By linking three LIKE conditions with OR, it retrieves data where the customer's state is either "California", "Oregon", or "Washington", hence obtaining customer records related to the west coast operations.
SQL Question 10: What is the purpose of the SQL constraint ?
The constraint makes sure that all values in a column are distinct. It is often paired with other constraints, like , to ensure that the data follows certain rules.
For example, say you were an analyst on the marketing team at United Natural Foods, and had access to a database on marketing campaigns:
In this example, the constraint is applied to the field to ensure that each campaign has a unique name. This helps to ensure the integrity of the data in the table and prevents errors that could occur if two campaigns had the same name.
SQL Question 11: Analyzing Customer Purchases and their Locations
You've been hired as a data analyst for United Natural Foods. They're interested in understanding the correlation between their customer's purchasing behavior and their geographical locations. Given two tables, and , can you write a SQL query to calculate the total purchase amount by state and the average purchase amount by state?
The table contains information about each customer, including their , , , and . The table contains all transactions made by customers, including , , , and .
Example Input:
| customer_id | first_name | last_name | state |
|---|---|---|---|
| 1602 | John | Doe | California |
| 2507 | Jane | Smith | Texas |
| 3645 | Alex | Johnson | New York |
| 4501 | Emma | Miller | California |
| 5242 | Oliver | Davis | Texas |
Example Input:
| purchase_id | customer_id | product_id | purchase_date | amount |
|---|---|---|---|---|
| 3745 | 1602 | 205 | 06/05/2022 | $200 |
| 4626 | 2507 | 1012 | 07/10/2022 | $150 |
| 5893 | 3645 | 230 | 06/01/2022 | $250 |
| 6547 | 4501 | 205 | 05/31/2022 | $100 |
| 7292 | 5242 | 1012 | 07/12/2022 | $300 |
Answer:
This SQL query uses a Join operation to connect the table with the table using as the common attribute. The function is used to calculate the total purchase amount by state, and function is used to calculate the average purchase amount by state. The result is grouped by and ordered in descending order of .
Since joins come up so often during SQL interviews, practice this Spotify JOIN SQL question:
United Natural Foods SQL Interview Tips
The best way to prepare for a United Natural Foods SQL interview is to practice, practice, practice. Beyond just solving the earlier United Natural Foods SQL interview questions, you should also solve the 200+ SQL exercises on DataLemur which come from companies like Google, Uber, and Microsoft.
Each SQL question has multiple hints, fully explained answers along with a discussion board to see how others solved it and crucially, there is an interactive coding environment so you can instantly run your query and have it checked.
To prep for the United Natural Foods SQL interview it is also a great idea to solve SQL questions from other food and facilities companies like:
- US Foods SQL questions
- Performance Food Group SQL questions
- Sysco SQL questions
- Peloton SQL questions
However, if your SQL skills are weak, don't worry about diving straight into solving questions – improve your SQL foundations with this free SQL tutorial.
This tutorial covers SQL topics like rank window functions and filtering data with WHERE – both of these pop up routinely in United Natural Foods interviews.
United Natural Foods Data Science Interview Tips
What Do United Natural Foods Data Science Interviews Cover?
In addition to SQL query questions, the other types of problems tested in the United Natural Foods Data Science Interview are:
- Statistics and Probability Questions
- Python or R Coding Questions
- Product Metrics Interview Questions
- ML Modelling Questions
- Behavioral Interview Questions
How To Prepare for United Natural Foods Data Science Interviews?
To prepare for the United Natural Foods Data Science interview have a strong understanding of the company's culture and values – this will be important for acing the behavioral interview. For the technical Data Science interviews, get ready by reading Ace the Data Science Interview. The book's got:
- 201 Interview Questions from tech companies like Netflix, Google, & Airbnb
- A Crash Course on Product Analytics, SQL & ML
- Great Reviews (1000+ reviews, 4.5-star rating)