11 WESCO SQL Interview Questions (Updated 2024)
Data Science, Data Engineering, and Data Analytics employees at WESCO use SQL to analyze sales trends, allowing them to identify peak purchasing periods and customer preferences. SQL is also used to predict inventory needs by examining historical data and current market demands, ensuring that stock levels align with customer needs, this is the reason why WESCO tests jobseekers on SQL coding interview questions.
So, to help you practice, we've curated 11 WESCO International SQL interview questions – can you solve them?
11 WESCO International SQL Interview Questions
SQL Question 1: Identify the VIP Customers of WESCO
WESCO is a company which sells electrical, industrial, and communications MRO and OEM products, construction materials, and advanced supply chain management and logistics services. As a data analyst at WESCO, your task is to identify the VIP Customers based on their purchasing frequency and total spending. VIP customers are defined as those who made purchases more than 50 times in a year and also have a total spending of over $50,000 within the same period. Write a SQL query to retrieve the list of such VIP Customers.
Example Input:
| purchase_id | customer_id | purchase_date | product_id | total_amount |
|---|---|---|---|---|
| 7651 | 101 | 04/08/2021 | 39801 | $1000 |
| 9822 | 202 | 04/16/2021 | 98945 | $3000 |
| 1323 | 101 | 04/18/2021 | 94089 | $2000 |
| 2589 | 301 | 04/22/2021 | 68092 | $1000 |
| 6005 | 101 | 04/30/2021 | 39801 | $1500 |
Answer:
This SQL query will first filter out the records of the year 2021. It will then group the records by and calculate the count of (frequency of purchases) and sum of (total spending) for each customer. Finally, it only includes the customers who making more than 50 purchases and spending more than $50000 in the output.
To solve a related super-user data analysis question on DataLemur's free online SQL code editor, try this recently asked Microsoft SQL interview question:
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SQL Question 2: Department vs. Company Salary
Suppose you had a table of WESCO employee salaries, along with which department they were in. Write a query to compare the average salary of employees in each department to the company's average salary. Return the comparison result as 'higher', 'lower', or 'same' for each department. Display the department ID, payment month (in MM-YYYY format), and the comparison.
Solve this question directly within the browser on DataLemur:
The answer is LONG – 30+ lines of SQL. You can find a detailed solution here: Department Salaries.
SQL Question 3: Can you list the various types of joins in SQL, and describe their purposes?
In SQL, a join retrieves rows from multiple tables and combines them into a single result set.
Four JOIN types can be found in SQL. For an example of each one, suppose you had a table of WESCO orders and WESCO customers.
-
INNER JOIN: Rows from both tables are retrieved when there is a match in the shared key or keys. An between the and tables would return only rows where the in the table matches the in the table.
-
LEFT JOIN: A retrieves all rows from the left table (in this case, the table) and any matching rows from the right table (the table). If there is no match in the right table, NULL values will be returned for the right table's columns.
-
RIGHT JOIN: A combines all rows from the right table (in this case, the table) and any matching rows from the left table (the table). If there is no match in the left table, NULL values will be displayed for the left table's columns.
-
FULL OUTER JOIN: A combines all rows from both tables, regardless of whether there is a match in the shared key or keys. If there is no match, NULL values will be displayed for the columns of the non-matching table.
SQL Question 4: Top Selling Products in the Last 5 Months
Write a SQL query to find the top 3 selling products for each employee in the sales team at WESCO for each of the last 5 months. Assume we have a table containing sale records and an table containing employee details.
Example of the table:
| sale_id | product_id | employee_id | quantity | sale_date |
|---|---|---|---|---|
| 1 | 1001 | 5001 | 25 | 2022-07-01 |
| 2 | 1002 | 5002 | 30 | 2022-07-02 |
| 3 | 1003 | 5001 | 15 | 2022-07-03 |
| 4 | 1001 | 5002 | 35 | 2022-07-04 |
| 5 | 1002 | 5001 | 10 | 2022-07-05 |
| 6 | 1003 | 5002 | 20 | 2021-06-01 |
Example of table:
| employee_id | name | role |
|---|---|---|
| 5001 | John Doe | Sales |
| 5002 | Jane Smith | Sales |
Answer:
In the above query, we first calculate the total quantity sold for each product by each employee for each month. Using a window function we then rank the products for each employee in each month based on the quantity sold, and finally filter for the top three products for each employee in each month.
To solve another window function question on DataLemur's free online SQL coding environment, try this Amazon SQL question asked in a BI Engineer interview:
SQL Question 5: What do the SQL commands / do?
For a tangible example of in PostgreSQL, suppose you were doing an HR Analytics project for WESCO, and had access to WESCO's contractors and employees data. Assume that some employees were previously contractors, and vice versa, and thus would show up in both tables.
You could use operator to find all contractors who never were a employee using this query:
Note that is available in PostgreSQL and SQL Server, while is the equivalent operator which is available in MySQL and Oracle (but don't worry about knowing which RDBMS supports which exact commands since WESCO interviewers aren't trying to trip you up on memorizing SQL syntax).
SQL Question 6: Order and Stock Management
WESCO, a company that manages a variety of electrical, industrial, and communications MRO and OEM products, wants to optimize its stock and order management. They are particularly interested in understanding which products are more frequently ordered together, so they can appropriately manage their stock levels. Your task is to design a suitable database and implement a query that fetches the top 5 commonly ordered products along with each product.
Example Input:
| order_id | client_id | order_date |
|---|---|---|
| 1001 | 1234 | 2022/06/01 |
| 1002 | 5678 | 2022/06/02 |
| 1003 | 9012 | 2022/06/03 |
| 1004 | 1234 | 2022/06/04 |
| 1005 | 5678 | 2022/06/05 |
Example Input:
| order_id | product_id |
|---|---|
| 1001 | 1 |
| 1001 | 3 |
| 1001 | 5 |
| 1002 | 2 |
| 1002 | 3 |
| 1003 | 4 |
| 1004 | 1 |
| 1004 | 2 |
| 1004 | 3 |
| 1005 | 2 |
| 1005 | 4 |
Example Input:
| product_id | product_name |
|---|---|
| 1 | Wire-cutter |
| 2 | Insulation tape |
| 3 | Cable ties |
| 4 | Electrical wire |
| 5 | Terminal blocks |
Given the above tables, write a query to find the top 5 product pairs based on the frequency of their being ordered together.
Answer:
Below is a suggested PostgreSQL query:
This SQL query essentially joins the order_items table with itself to obtain pairs of products ordered together. Since we want distinct pairs and not permutations, we ensure that to avoid duplication. Finally, join with products table is performed to get product names and the results are sorted by frequency in descending order to get top 5 pairs.
SQL Question 7: What's the difference between and ?
Before we address vs. question, let's address the clause which is used in a statement to group rows into a set of summary rows. It's typically used in conjunction with aggregate functions such as:
- `MIN
The clause is used to filter the groups created by the clause. It's similar to the clause, but it is used to specify conditions on the groups created by the clause, rather than on the individual rows of the table.
For example:
This query retrieves the total salary for each department and groups the rows by department. The clause then filters the groups to include only WESCO departments where the total salary is greater than $1 million
Note that the clause must be used after the clause and can only reference columns listed in the clause or aggregated columns selected by the statement.
SQL Question 8: Calculate the Average Sale Price Per Item Category in WESCO
Consider that you are working as a Data Analyst at WESCO, a leading distributor of electrical, communications and data networking products. You've been tasked with writing a SQL query to calculate the average selling price of each product category.
Below is some sample data of the and tables:
Example Input:
| product_id | product_name | category |
|---|---|---|
| 1001 | Siemon Cat5e Jack | Network Equipment |
| 1002 | Cisco Switch 3500 | Network Equipment |
| 2001 | Square D Circuit Breaker | Industrial Equipment |
Example Input:
| sale_id | product_id | sale_date | sale_price |
|---|---|---|---|
| 1101 | 1001 | 01/05/2022 00:00:00 | $32 |
| 2101 | 2001 | 02/18/2022 00:00:00 | $120 |
| 1102 | 1001 | 03/08/2022 00:00:00 | $30 |
| 2201 | 2001 | 04/15/2022 00:00:00 | $130 |
| 1201 | 1002 | 05/22/2022 00:00:00 | $105 |
The SQL query to solve it is:
Answer:
This PostgreSQL query will solve the problem by joining the and tables on , and then grouping the results by . The function is used to calculate the average for each category. The result will be the average selling price of each product category in WESCO.
To practice a very similar question try this interactive Amazon Highest-Grossing Items Question which is similar for calculating top performing products by category or this Wayfair Y-on-Y Growth Rate Question which is similar for understanding sales data over time.
SQL Question 9: Find total sales for each product category
As a Data Analyst at WESCO, your manager has requested that you determine the total sales for each product category in the last quarter. Each sale in the table has a , , and .
Additionally, there is a table where each is associated with a .
Please write an SQL query which can answer this question.
Example Input:
| sale_id | time_stamp | product_id | sale_price |
|---|---|---|---|
| 101 | 2022-07-15 14:30:00 | 1 | 100.00 |
| 102 | 2022-07-15 15:00:00 | 2 | 200.00 |
| 103 | 2022-08-15 11:30:00 | 1 | 150.00 |
| 104 | 2022-09-10 09:00:00 | 3 | 300.00 |
| 105 | 2022-09-15 14:50:00 | 3 | 250.00 |
Example Input:
| product_id | product_category |
|---|---|
| 1 | 'Electrical equipment' |
| 2 | 'Lighting' |
| 3 | 'Security' |
Answer:
This query first joins the table with the table on the . It then restricts to rows where the is in the last quarter. Finally, it groups by and sums the within each group to get the total sales for each product category.
SQL Question 10: What's a database view?
Database views are created to provide customized, read-only versions of your data that you can query just like a regular table. So why even use one if they're just like a regular table?
Views are useful for creating a simplified version of your data for specific users, or for hiding sensitive data from certain users while still allowing them to access other data.
SQL Question 11: Search Customer Records
The table for WESCO contains information related to their customers. Sometimes, the customer support team needs to retrieve the records for all customers that have a email. Can you write an SQL query that will retrieve the records for all customers whose email ends with ?
Example Input:
| customer_id | first_name | last_name | address | |
|---|---|---|---|---|
| 1 | John | Smith | john.smith@gmail.com | 123 Elm Street |
| 2 | Jane | Doe | jane_doe@yahoo.net | 456 Oak Street |
| 3 | Mary | Johnson | mary.johnson@jmail.com | 789 Maple Street |
| 4 | James | Brown | jbrown@wesco.com | 321 Pine Street |
| 5 | Emily | Davis | edavis@outlook.net | 654 Birch Street |
Example Output:
| customer_id | first_name | last_name | address | |
|---|---|---|---|---|
| 1 | John | Smith | john.smith@gmail.com | 123 Elm Street |
| 3 | Mary | Johnson | mary.johnson@jmail.com | 789 Maple Street |
| 4 | James | Brown | jbrown@wesco.com | 321 Pine Street |
Answer:
This query uses the keyword in SQL, in combination with the wildcard character, to search for a pattern in the field of the table. Specifically, it retrieves all records where the field ends with . The character is used to represent zero, one or multiple characters. Therefore, the pattern will match any string that ends with .
How To Prepare for the WESCO SQL Interview
The key to acing a WESCO SQL interview is to practice, practice, and then practice some more! Besides solving the earlier WESCO SQL interview questions, you should also solve the 200+ SQL questions on DataLemur which come from companies like Netflix, Google, and Amazon.
Each interview question has hints to guide you, full answers and best of all, there is an interactive coding environment so you can easily right in the browser your query and have it checked.
To prep for the WESCO SQL interview it is also helpful to practice interview questions from other industrial and electrical distribution companies like:
However, if your SQL coding skills are weak, forget about diving straight into solving questions – strengthen your SQL foundations with this interactive SQL tutorial.
This tutorial covers topics including handling strings and LEFT vs. RIGHT JOIN – both of which come up often in SQL job interviews at WESCO.
WESCO International Data Science Interview Tips
What Do WESCO Data Science Interviews Cover?
Beyond writing SQL queries, the other question categories tested in the WESCO Data Science Interview include:
- Probability & Statistics Questions
- Python Pandas or R Coding Questions
- Product Metrics Interview Questions
- Machine Learning Questions
- Resume-Based Behavioral Questions
How To Prepare for WESCO Data Science Interviews?
I believe the optimal way to study for WESCO Data Science interviews is to read the book Ace the Data Science Interview.
It solves 201 data interview questions taken from companies like Google, Tesla, & Goldman Sachs. The book's also got a crash course on Stats, SQL & ML. And finally it's helped thousands of people land their dream job in data, which is how it's gotten to be an Amazon best-seller with over 1000+ 5-star reviews.
While the book is more technical, it's also key to prepare for the WESCO behavioral interview. A good place to start is by understanding the company's values and company principles.