8 Darling Ingredients SQL Interview Questions (Updated 2024)
Data Science, Data Engineering, and Data Analytics employees at Darling Ingredients use SQL to extract and analyze data from their large supply chain network, helping them optimize processes and improve efficiency. They also rely on SQL to manage data related to their sustainable solutions development, ensuring they stay committed to eco-friendly practices, this is the reason why Darling Ingredients often asks jobseekers with SQL coding interview questions.
Thus, to help you prep for the Darling Ingredients SQL interview, we'll cover 8 Darling Ingredients SQL interview questions – can you solve them?
8 Darling Ingredients SQL Interview Questions
SQL Question 1: Identify the Top Purchasing Customers at "Darling Ingredients"
Darling Ingredients is a provider of food ingredient solutions. Let's say the most critical activity to the business is the frequency of purchasing products, and hence, a 'power user' or 'VIP user' is considered to be a customer who very frequently purchases their products.
Your goal is to write a SQL query to identify the top 5 customers who had the highest number of purchases in the last year.
Consider the following two tables:
Example Input:
| customer_id | customer_name |
|---|---|
| 101 | John |
| 102 | Michael |
| 103 | Sarah |
| 104 | Emma |
| 105 | Robert |
Example Input:
| purchase_id | customer_id | product_id | purchase_date |
|---|---|---|---|
| 5001 | 101 | 325 | 06/10/2021 |
| 5002 | 103 | 347 | 06/15/2021 |
| 5003 | 101 | 325 | 07/05/2021 |
| 5004 | 102 | 369 | 08/20/2021 |
| 5005 | 101 | 325 | 09/05/2021 |
| 5006 | 105 | 385 | 10/26/2021 |
| 5007 | 101 | 369 | 11/05/2021 |
| 5008 | 103 | 325 | 01/25/2022 |
| 5009 | 102 | 369 | 03/21/2022 |
| 5010 | 103 | 347 | 05/15/2022 |
Answer:
The following PostgreSQL statement can be used to solve this:
This query first combines data from the 'customers' and 'purchases' tables using an INNER JOIN on the common 'customer_id' field. Then it restricts the data to purchases made within the last year using a WHERE clause. The result set is grouped by 'customer_name', with the number of purchases calculated for each customer. The query then orders the result in descending order of number of purchases and finally limits the output to the top 5 customers.
To practice a similar customer analytics SQL question where you can solve it interactively and have your SQL solution instantly graded, try this Walmart SQL Interview Question:
Check out Darling Ingredients' news releases to stay informed about their latest innovations and sustainability efforts in the food and agriculture sectors! Understanding Darling Ingredients' initiatives can provide valuable insights into how they are working towards a more sustainable future.
SQL Question 2: Employee Salaries Higher Than Their Manager
Given a table of Darling Ingredients employee salary data, write a SQL query to find employees who earn more money than their own boss.
Darling Ingredients 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.
Try this 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 code above is hard to understand, you can find a step-by-step solution here: Highly-Paid Employees.
SQL Question 3: What's a primary key?
A primary key is a column or set of columns in a table that uniquely identifies each row in the table. The primary key is used to enforce the uniqueness and non-nullability of the rows in the table.
In a SQL database, a primary key is defined using the constraint. For example, say you had a table of :
In this example, the column is the primary key of the Darling Ingredients employees table. It is defined as an integer and is marked as the primary key using the constraint.
A table can have only one primary key, but the primary key can consist of multiple columns. For example, say you had a table of Darling Ingredients customer transactions:
In the above example, the primary key of the Orders table consists of two columns: TransactionID and ProductID. This means that the combination of OrderID and ProductID must be unique for every row in the table.
SQL Question 4: Analyze Sales Data by Month and Product
As an analyst at Darling Ingredients, you are being asked to analyze the sales data and come up with the total revenue generated from the sale of each product every month. You are given the Sales table with details about each transaction. Can you write a SQL query to generate a table that provides the product_id, the month, and the total revenue generated from the sale of each product each month? Please, use a window function in your query.
Below is the provided "Sales" table:
Example Input:
| transaction_id | transaction_date | product_id | price | quantity |
|---|---|---|---|---|
| 5837 | 01/25/2022 00:00:00 | P300 | 10.99 | 5 |
| 7682 | 01/29/2022 00:00:00 | P301 | 20.50 | 3 |
| 5678 | 02/10/2022 00:00:00 | P302 | 30.20 | 6 |
| 5349 | 02/18/2022 00:00:00 | P300 | 10.99 | 5 |
| 6374 | 02/25/2022 00:00:00 | P301 | 20.50 | 2 |
Answer:
This query first computes the revenue from each transaction (price * quantity) in the subquery. The outer query then calculates the total revenue per product and month using a window function (SUM() OVER), partitioned by product_id and month. The result is ordered by product_id and month to provide a quick overview of how the revenue per product evolved over time. This information can be used to evaluate sales strategies, make predictions and take pertinent decisions.
To solve a related window function SQL problem on DataLemur's free online SQL code editor, try this Google SQL Interview Question:
SQL Question 5: What's the difference between a foreign and primary key?
To better understand the difference between a primary key and a foreign key, let's use an example from Darling Ingredients's marketing analytics database, which holds data on Google Ads campaigns:
:
| ad_id | campaign_id | keyword | click_count |
|---|---|---|---|
| 1 | 100 | Darling Ingredients pricing | 10 |
| 2 | 100 | Darling Ingredients reviews | 15 |
| 3 | 101 | Darling Ingredients alternatives | 7 |
| 4 | 101 | buy Darling Ingredients | 12 |
In this table, serves as the primary key. It uniquely identifies each ad and cannot be null.
is a foreign key that connects to the of the corresponding Google Ads campaign. This establishes a relationship between the ads and their campaigns, enabling easy querying to find which ads belong to a specific campaign or which campaigns a specific ad belongs to.
The table may also have multiple foreign keys that reference primary keys in other tables. For example, and foreign keys could be used to link each ad to its ad group and the Google Ads account that the campaigns belong to, respectively.
SQL Question 6: Calculate Monthly Average Ingredient Costs
Darling Ingredients produces sustainable natural ingredients from edible and inedible bio-nutrients. This includes a variety of materials such as fats, proteins, and hides. Let's say you are given a database containing the purchase details of each ingredient. Each purchase is recorded with an acquisition cost, the amount in kilograms, and the date of acquisition.
Your task is to write an SQL query which finds the average cost of all ingredients bought, per kilogram, per month.
Example Input:
| ingredient_id | acquisition_date | acquisition_cost_dollar | amount_kg |
|---|---|---|---|
| 1 | 01/10/2022 | 3000 | 250 |
| 2 | 01/10/2022 | 1500 | 100 |
| 3 | 01/30/2022 | 2000 | 150 |
| 4 | 02/12/2022 | 500 | 50 |
| 5 | 02/20/2022 | 1000 | 100 |
| 6 | 03/01/2022 | 3500 | 200 |
Example Output:
| month | avg_cost_per_kg |
|---|---|
| 01 | 11.54 |
| 02 | 15.00 |
| 03 | 17.50 |
Answer:
This SQL query first uses the function to extract the month from the acquisition date. Then, it calculates the cost per kilogram for each ingredient purchase by dividing the acquisition cost by the amount in kilograms. Finally, the and functions calculate the monthly average cost per kilogram. Note that the function is used to limit the average cost to two decimal places. The results are sorted by month.
SQL Question 7: Can you describe a cross-join and its purpose?
A cross-join, also known as a cartesian join, is a type of join that returns the cross-product of two tables. In a cross-join, each row from the first table is paired with every row from the second table, resulting in a new table that has a row for each possible combination of rows from the two input tables.
For example, say you worked on the Marketing Analytics team at Darling Ingredients, and needed to understand what advertising copy (text) goes best with what advertising creative (the photo that gets posted with the advertisement copy).
Here is an example of a cross-join between a table of ad_copy and a table of ad_creative:
You could this query to generate all possible combinations of ad copy and ad creative to help you create more effective ads for Darling Ingredients. Just be careful: if you had 1,000 rows of ad copy and 1,000 different image creatives, the resulting cross-join would have 1 million rows!
SQL Question 8: Find Customers with a Specific Pattern in Their Names
Darling Ingredients is a global leader in creating sustainable food, feed and fuel ingredients. In their business, they often have to filter customer records to find specific customers. As a database manager, your task is to find all customers who have the string 'darl' anywhere in their names, irrespective of case.
Example Input:
| customer_id | customer_name | registration_date | product_id | location |
|---|---|---|---|---|
| 1001 | Darla Morton | 01/12/2021 00:00:00 | 40001 | Texas |
| 2053 | John Darling | 02/24/2022 00:00:00 | 45892 | Arizona |
| 3078 | David Carlson | 03/18/2022 00:00:00 | 40001 | California |
| 4150 | Adele Darling | 04/26/2022 00:00:00 | 45892 | New York |
| 5071 | Tiffany Jordan | 05/05/2021 00:00:00 | 45892 | Texas |
Answer:
This simple SQL query will return all the records from the 'customer' table where the customer's name contains the string 'darl', irrespective of case. The '%' on either side of 'darl' in the LIKE clause specifies that 'darl' can appear anywhere in the name, and the LOWER() function is used to ensure the search is case-insensitive.
How To Prepare for the Darling Ingredients SQL Interview
The best way to prepare for a Darling Ingredients SQL interview is to practice, practice, practice. In addition to solving the earlier Darling Ingredients SQL interview questions, you should also solve the 200+ SQL Interview Questions on DataLemur which come from companies like Amazon, JP Morgan, and food and facilities companies like Darling Ingredients.
Each DataLemur SQL question has hints to guide you, detailed solutions and crucially, there's an interactive coding environment so you can right in the browser run your query and have it executed.
To prep for the Darling Ingredients SQL interview you can also be helpful to practice interview questions from other food and facilities companies like:
- Sanderson Farms SQL questions
- Monster Beverage SQL questions
- Coca-Cola SQL questions
- Post Holdings SQL questions
However, if your SQL coding skills are weak, don't worry about jumping right into solving questions – improve your SQL foundations with this free SQL for Data Analytics course.
This tutorial covers things like joining multiple tables and window functions – both of these pop up routinely in Darling Ingredients SQL assessments.
Darling Ingredients Data Science Interview Tips
What Do Darling Ingredients Data Science Interviews Cover?
In addition to SQL interview questions, the other topics to practice for the Darling Ingredients Data Science Interview are:
- Statistics and Probability Questions
- Python or R Programming Questions
- Product-Sense and Business Case Questions
- ML Modelling Questions
- Resume-Based Behavioral Questions
How To Prepare for Darling Ingredients Data Science Interviews?
To prepare for the Darling Ingredients Data Science interview have a strong understanding of the company's values and company principles – this will be key to acing the behavioral interview. For technical interviews prepare by reading Ace the Data Science Interview. The book's got:
- 201 Interview Questions from tech companies like Google & Microsoft
- A Crash Course on Python, SQL & ML
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