8 STMicroelectronics SQL Interview Questions (Updated 2024)
At STMicroelectronics, SQL is used quite frequently for analyzing semiconductor manufacturing data for quality control and tracking supply chain operations to optimize inventory management. Unsurprisingly this is why STMicroelectronics often tests SQL problems in interviews for Data Science, Analytics, and & Data Engineering jobs.
So, to help you prepare for the STMicroelectronics SQL interview, we've collected 8 STMicroelectronics SQL interview questions – how many can you solve?
8 STMicroelectronics SQL Interview Questions
SQL Question 1: Identify Power Users in STMicroelectronics
STMicroelectronics is a global semiconductor leader that designs and manufactures a wide range of integrated circuits and microcontrollers. The number of orders placed by a user are a good measure to identify the 'Power Users' or 'VIP Users'. Let us assume that STMicroelectronics wants to identify such users who have placed more than 100 orders in the previous month.
Here's the schema for the Users and Orders tables:
Table:
| user_id | user_name | user_address |
|---|---|---|
| 101 | John Doe | 202, Maple Street, Boston |
| 102 | Jane Doe | 101, Elm Street, New York |
| 103 | Andreas Muller | 164, Lehmweg, Hamburg |
| 104 | Alice Brown | 303, Oak Street, Seattle |
| 105 | Yuki Sato | 202, Cherry Blossom Ave, Tokyo |
Table:
| order_id | user_id | order_date | product_id | quantity |
|---|---|---|---|---|
| 50101 | 101 | 06/10/2022 00:00:00 | 10001 | 1000 |
| 50102 | 101 | 06/20/2022 00:00:00 | 10002 | 500 |
| 50103 | 102 | 06/18/2022 00:00:00 | 10001 | 300 |
| 50104 | 101 | 06/30/2022 00:00:00 | 10003 | 700 |
| 50105 | 103 | 07/05/2022 00:00:00 | 10002 | 900 |
Your task is to write a PostgreSQL query to identify the 'Power Users' who have placed over 100 orders in the last month.
Answer:
This query will return the IDs and names of all users who have placed over 100 orders in the previous month. The subquery filters the Orders table for orders from the last month, groups them by user_id and counts the number of orders per user. The clause then filters for users with more than 100 orders. The output of the subquery is then joined with the Users table on user_id to get the user details.
To practice a super-customer analysis question on DataLemur's free online SQL coding environment, try this Microsoft Azure Cloud SQL Interview Question:
SQL Question 2: Monthly Average Sales of Semiconductor Products
STMicroelectronics, being a leader in the semiconductor industry, maintains a detailed log of all product sales. You are given a dataset consisting of monthly sales data of different chip models. The company would like to calculate the monthly average number of units sold for each chip model over a given period.
Assume you have the following table named :
Example Input:
| sale_id | date | chip_model | units_sold |
|---|---|---|---|
| 501 | 2022-06-08 | STM32F4 | 100 |
| 502 | 2022-06-20 | STM32F4 | 150 |
| 503 | 2022-07-01 | STM32F1 | 120 |
| 504 | 2022-07-17 | STM8L10 | 220 |
| 505 | 2022-07-25 | STM32F4 | 180 |
STMicroelectronics would like an output in the following format, showing the average units sold per model per month:
Example Output:
| month | chip_model | avg_units_sold |
|---|---|---|
| 6 | STM32F4 | 125.00 |
| 7 | STM32F1 | 120.00 |
| 7 | STM8L10 | 220.00 |
| 7 | STM32F4 | 180.00 |
Answer:
Here is an SQL query using PostgreSQL syntax that solves this problem. We will use the function to extract the month from the date column, and then we will group by the month and chip model to calculate the average.
This query truncates the date to the nearest month, groups the data by the month and chip model, and then applies the function to calculate the average units sold per month for each chip model. Then it orders the results by month and average units sold in descending order to bring the best-selling chip models to the top.
To practice another window function question on DataLemur's free interactive SQL code editor, solve this Google SQL Interview Question:
SQL Question 3: What's the difference between a foreign and primary key?
To explain the difference between a primary key and foreign key, let's start with some data from STMicroelectronics's marketing analytics database which stores data from Google Ads campaigns:
:
+------------+------------+------------+------------+ | ad_id | campaign_id| keyword | click_count| +------------+------------+------------+------------+ | 1 | 100 | STMicroelectronics pricing | 10 | | 2 | 100 | STMicroelectronics reviews | 15 | | 3 | 101 | STMicroelectronics alternatives | 7 | | 4 | 101 | buy STMicroelectronics | 12 | +------------+------------+------------+------------+
In this table, could be a primary key. It is unique for each row in the table and cannot contain null values.
could be 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 4: Filter Customer Records Based on Purchase Volume and Region
In STMicroelectronics, a leading global semiconductor company, you're given access to a customer records database. You need to create a list of customers that are from either North America or Europe (EU) and have purchased more than 500 units of any product in the last year (2021). You're asked to exclude customers who have returned more than 50 units.
Example Input
Example Input
Example Input
Answer:
This SQL query first calculates the total units purchased and returned by each customer in 2021. It then joins these calculations with the customers table to filter down the customers based on region, total purchase, and total returns. It only selects customers from North America or EU who have purchased over 500 units and returned less than or equal to 50 units.
SQL Question 5: What does do, and when would you use this SQL command?
combines the results from two or more SELECT statements, but only returns the rows that are exactly the same between the two sets.
For example, say you were doing an HR Analytics project for STMicroelectronics, and had access to STMicroelectronics'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 employees who also show up in the contractors table:
SQL Question 6: Calculate the Click-Through-Rate for Marketing Campaigns
STMicroelectronics conducts various marketing campaigns for its electronic components. We track information about impressions, the number of times an ad was shown, and clicks, the number of times the ad was clicked.
The click-through rate (CTR) is a key metric used to measure the success of these campaigns. This is calculated as the number of clicks divided by the number of impressions, multiplied by 100 to give a percentage.
Given tables and , write a SQL query to calculate the CTR for each marketing campaign.
Example Input:
| campaign_id | name | start_date | end_date | impressions |
|---|---|---|---|---|
| 101 | CampaignA | 01/01/2022 | 01/02/2022 | 1500 |
| 102 | CampaignB | 01/10/2022 | 01/15/2022 | 4500 |
| 103 | CampaignC | 02/01/2022 | 02/05/2022 | 3000 |
| 104 | CampaignD | 02/15/2022 | 02/20/2022 | 2000 |
Example Input:
| click_id | campaign_id | click_time |
|---|---|---|
| 50101 | 101 | 01/01/2022 10:10:10 |
| 50102 | 101 | 01/01/2022 10:11:12 |
| 50103 | 102 | 01/10/2022 15:12:13 |
| 50104 | 103 | 02/01/2022 16:12:14 |
| 50105 | 103 | 02/02/2022 16:12:15 |
| 50106 | 103 | 02/02/2022 16:20:15 |
| 50107 | 104 | 02/15/2022 15:10:12 |
| 50108 | 104 | 02/16/2022 12:20:10 |
Answer:
Here is a SQL query that calculates the CTR for each campaign. This query first counts the number of clicks for each campaign, then calculates the CTR by dividing the number of clicks by the number of impressions.
This query will return a table that lists each campaign by its ID and name along with the number of impressions, the number of clicks and the calculated CTR. The campaigns are sorted by CTR in descending order.
To practice a similar SQL interview question on DataLemur's free interactive SQL code editor, attempt this SQL interview question asked by Facebook:
SQL Question 7: What's the difference between relational and NoSQL databases?
While knowing this answer is beyond the scope of most Data Analyst & Data Science interviews, Data Engineers at STMicroelectronics should be at least aware of SQL vs. NoSQL databases.
Relational databases and non-relational (NoSQL) databases have some key differences, particularly in terms of how data is stored. Whereas relational databases have tables, made up of rows and columns, NoSQL databases use various data models like:
- Wide-Column Stores – this database uses tables, rows, and columns, but unlike a relational database, the names and format of the columns can vary from row to row within the same table
- Key-Value Stores – instead of rows and columns, you have keys, where each key is associated with only one value in a collection (similar to a Python dictionary data structure!)
- Graph Stores – instead of rows of data, you have nodes, and then can also have edges between entities (much like a Graph Data Structure for those who've taken a Computer Science data structures & algorithms class)
This added flexibility makes NoSQL databases well-suited for handling non-tabular data or data with a constantly changing format. However, this flexibility comes at the cost of ACID compliance, which is a set of properties (atomic, consistent, isolated, and durable) that ensure the reliability and integrity of data in a database. While most relational databases are ACID-compliant, NoSQL databases may not provide the same level of guarantees.
SQL Question 8: Filter Customers Based on Status
STMicroelectronics is a global semiconductor leader delivering intelligent and energy-efficient products and solutions. As a part of their customer management, the company maintains a customer records database. Your task is to write an SQL query that filters the customers to display only those whose status is marked as "Active" and whose names start with the letter 'S'.
As an example, here's a snapshot of how the table is expected to look:
Example Input:
| customer_id | first_name | last_name | status | |
|---|---|---|---|---|
| 1 | John | Doe | johndoe@example.com | Active |
| 2 | Sarah | Smith | sarahsmith@example.com | Active |
| 3 | Samuel | Jackson | samuelj@somemail.com | Inactive |
| 4 | Sandra | Bullock | sbullock@example.com | Active |
| 5 | Steve | Jobs | stevejobs@apple.com | Inactive |
| 6 | Simon | Williams | simonw@example.com | Active |
Your SQL query should return:
Example Output:
| customer_id | first_name | last_name | status | |
|---|---|---|---|---|
| 2 | Sarah | Smith | sarahsmith@example.com | Active |
| 4 | Sandra | Bullock | sbullock@example.com | Active |
| 6 | Simon | Williams | simonw@example.com | Active |
Answer:
This SQL query filters the customers table to select all columns () where the status equals 'Active' () and the first name begins with the letter 'S' (). The % is a wildcard character in SQL's LIKE clause, which matches any sequence of characters. Thus, 'S%' matches any string that starts with 'S'.
STMicroelectronics SQL Interview Tips
The best way to prepare for a STMicroelectronics SQL interview is to practice, practice, practice.
Besides solving the above STMicroelectronics SQL interview questions, you should also solve the 200+ DataLemur SQL Interview Questions which come from companies like Google, Microsoft and Silicon Valley startups.
Each problem on DataLemur has hints to guide you, detailed solutions and most importantly, there is an interactive SQL code editor so you can instantly run your SQL query and have it checked.
To prep for the STMicroelectronics SQL interview it is also a great idea to practice SQL questions from other semiconductor companies like:
However, if your SQL query skills are weak, don't worry about diving straight into solving questions – refresh your SQL knowledge with this free SQL for Data Analytics course.
This tutorial covers SQL concepts such as finding NULLs and RANK() window functions – both of these pop up often during STMicroelectronics SQL assessments.
STMicroelectronics Data Science Interview Tips
What Do STMicroelectronics Data Science Interviews Cover?
Beyond writing SQL queries, the other types of questions to practice for the STMicroelectronics Data Science Interview are:
- Probability & Stats Questions
- Coding Questions in Python or R
- Open-Ended Data Case Studies
- Machine Learning and Predictive Modeling Questions
- Behavioral Based Interview Questions
How To Prepare for STMicroelectronics Data Science Interviews?
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