9 Hesai Technology SQL Interview Questions (Updated 2024)
Data Analytics, Data Science, and Data Engineering employees at Hesai Technology write SQL queries all the time as part of their job. They use SQL for analyzing sensor data for pattern detection, and managing databases for efficient storage and retrieval of LiDAR technology data. Because of this, Hesai Technology typically asks folks interviewing for data jobs SQL coding interview questions.
So, to help you study for the Hesai Technology SQL interview, here’s 9 Hesai Group SQL interview questions in this blog.
9 Hesai Group SQL Interview Questions
SQL Question 1: Identify High-Value Customers at Hesai Technology
Suppose Hesai Technology is an online e-commerce platform and the main business goal is to identify the top purchasing customers (i.e., whale users) based on the total purchasing amount in the past month across all product categories. Write a SQL query that can retrieve these customers along with the total spend.
Example Input:
| order_id | user_id | order_date | product_id | amount |
|---|---|---|---|---|
| 651 | 654 | 06/21/2023 00:00:00 | 1050 | 45.5 |
| 982 | 453 | 06/22/2023 00:00:00 | 9872 | 120.7 |
| 329 | 654 | 06/23/2023 00:00:00 | 2014 | 89.3 |
| 231 | 344 | 06/24/2023 00:00:00 | 5432 | 200.0 |
| 782 | 344 | 06/25/2023 00:00:00 | 7678 | 150.0 |
Example Input:
| user_id | name | |
|---|---|---|
| 654 | Alice | alice@hesai.tech |
| 453 | Bob | bob@hesai.tech |
| 344 | Clara | clara@hesai.tech |
| 112 | David | david@hesai.tech |
| 876 | Emma | emma@hesai.tech |
Answer:
The SQL query joins the and table on user_id to associate order details with each user. It then filters the orders for the past month, sums up the amount spent by each user, and orders the users by the total amount spent in descending order. The at the end will only return the top 5 customers that have spent the most in the past month. This allows businesses to identify and perhaps reward their highest value customers.
To practice another SQL customer analytics question where you can solve it right in the browser and have your SQL code instantly graded, try this Walmart Labs SQL Interview Question:
SQL Question 2: 2nd Largest Salary
Given a table of Hesai Technology employee salary information, write a SQL query to find the 2nd highest salary at the company.
Hesai Technology Example Input:
| employee_id | salary |
|---|---|
| 1 | 2500 |
| 2 | 800 |
| 3 | 1000 |
| 4 | 1200 |
Example Output:
| second_highest_salary |
|---|
| 1200 |
Check your SQL query for this problem and run your code right in the browser:
Answer:
You can find a detailed solution with hints here: 2nd Highest Salary.
SQL Question 3: Can you describe a cross-join and its purpose?
A cross-join, also known as a cartesian join, is like a mad scientist's laboratory experiment gone wild. It takes two tables and mixes them together to create a crazy new table with every possible combination of rows from the original tables.
Here's an example:
If you have 20 products and 10 colors, that's 200 rows right there! Cross-joins are great for generating all possible combinations, but they can also create really big tables if you're not careful. Just like a mad scientist, use your powers wisely!
SQL Question 4: Compute Sensor Failures by Month
Hesai Technology is a lidar (light detection and ranging) company that focuses on autonomous vehicles, robotics, and mapping. They have a detailed log of sensors they have sold, including the unique sensor id, the date it was sold and the date of its first failure. They want to produce an analysis of average monthly sensor failures. They need a SQL query that breaks down the average failures by each month.
Example Input:
| sensor_id | sold_date | failure_date |
|---|---|---|
| 10578 | 01/03/2022 00:00:00 | 03/07/2022 00:00:00 |
| 48962 | 01/02/2022 00:00:00 | 01/04/2022 00:00:00 |
| 78652 | 01/06/2022 00:00:00 | 01/08/2022 00:00:00 |
| 34251 | 01/04/2022 00:00:00 | 01/07/2022 00:00:00 |
| 96321 | 01/05/2022 00:00:00 | null |
Use the function to get the month from the date-time data. Use the function over the window partitioned by the month.
Answer:
This PostgreSQL query uses the window function to count the number of failures partitioned by the sale month of each sensor. So for each month, it counts the number of times sensors failed after being sold. The function is used to extract the month number from the dates in the 'sold_date' column. The counts the amount of non-null values in the 'failure_date' column - effectively counting the amount of sensor failures. Note that sensors that hasn't failed yet would have a NULL value for their 'failure_date'.
p.s. Window functions show up pretty often during SQL interviews, so practice the 27+ window function questions on DataLemur
SQL Question 5: Can you explain the distinction between a unique and a non-unique index?
Some similarities between unique and non-unique indexes include:
- Both types improve the performance of SQL queries by providing a faster way to lookup the desired data.
- Both types use an additional data structure to store the indexed data, which requires additional storage space which impacts write performance.
- Both types of indexes can be created on one or more columns of a table.
Some differences between unique and non-unique indexes include:
- A unique index enforces the uniqueness of the indexed columns, meaning that no duplicate values are allowed in the indexed columns. A non-unique index allows duplicate values in the indexed columns.
- A unique index can be used to enforce the primary key of a table, but a non-unique index cannot.
- A unique index can have a maximum of one NULL value in the indexed columns, but a non-unique index can have multiple NULLs
SQL Question 6: Sales Analysis for Lidar Products
Hesai Technology specializes in the development of high-performance LiDAR (Light Detection and Ranging) sensors for autonomous vehicles, industrial and environmental use. They are interested in understanding their sales performance better.
Design a database schema that comprises of 2 tables:
- - which contains product information.
- - which contains transactional sales data.
Given this schema, provide a SQL query that answers the following question:
- "What is the monthly sales volume and revenue for each product category for the current year?"
Example Input:
| product_id | category | product_name | unit_price |
|---|---|---|---|
| 001 | Automotive | LiDAR Sensor A1 | $1000 |
| 002 | Industrial | LiDAR Sensor B2 | $2000 |
| 003 | Environmental | LiDAR Sensor C3 | $1500 |
Example Input:
| sale_id | product_id | quantity | sale_date |
|---|---|---|---|
| P001 | 001 | 4 | 01/09/2022 |
| P002 | 002 | 3 | 05/09/2022 |
| P003 | 003 | 5 | 10/09/2022 |
| P004 | 001 | 2 | 15/09/2022 |
| P005 | 002 | 6 | 20/09/2022 |
Answer:
In PostgreSQL, you can extract month from date using the function. Below is a SQL query that answers the question:
The query begins by joining the table with the table on . It filters the sales data to include only transactions from the current year. It then groups the data by and , and calculates two aggregations for each group: (the sum of ) and (the product of and ). The final result is ordered by and . This will help Hesai to further decide their strategy accordingly.
SQL Question 7: What is a primary key?
A primary key is a column or group of columns that uniquely identifies a row in a table. For example, say you had a database of Hesai Technology marketing campaigns data:
In this Hesai Technology example, the CampaignID column is the primary key of the MarketingCampaigns table. The constraint ensures that no two rows have the same CampaignID. This helps to maintain the integrity of the data in the table by preventing duplicate rows.
SQL Question 8: Filtering Customer Records
Given a customer records database of Hesai Technology which stores details like the , , , and . Your task is to write an SQL query to filter customers who have purchased products after 1st January 2022, from location and the total transaction amount is greater than $500.
Example Input:
| customer_id | product_purchased | purchase_date | location | total_amount |
|---|---|---|---|---|
| 101 | Lidar Sensor | 03/15/2022 | California | 700 |
| 202 | Photonics Services | 11/30/2021 | Texas | 1500 |
| 303 | Lidar Sensor | 01/10/2022 | California | 550 |
| 404 | Photonics Services | 12/20/2021 | California | 487 |
| 505 | Lidar Sensor | 02/25/2022 | New York | 850 |
Answer:
This query filters the records from the table where the is after 1st January 2022, the is California, and the is greater than $500.
Example Output:
| customer_id | product_purchased | purchase_date | location | total_amount |
|---|---|---|---|---|
| 101 | Lidar Sensor | 03/15/2022 | California | 700 |
| 303 | Lidar Sensor | 01/10/2022 | California | 550 |
SQL Question 9: Filtering and Searching Employee Records
As a database manager at Hesai Technology, you are required to filter the employee records. Find employees from the Tech department whose first names start with "J" and their hire date is within the year 2020.
Example Input:
| employee_id | first_name | last_name | hire_date | department |
|---|---|---|---|---|
| 3032 | Jackson | Miller | 2020-05-15 | Tech |
| 4501 | Jonathan | Finn | 2019-09-01 | Marketing |
| 2981 | Jane | Doe | 2020-10-12 | Tech |
| 5720 | Doe | Johnson | 2020-03-19 | Admin |
| 8473 | John | Patel | 2020-08-11 | Tech |
Example Output:
| employee_id | first_name | last_name | hire_date | department |
|---|---|---|---|---|
| 3032 | Jackson | Miller | 2020-05-15 | Tech |
| 2981 | Jane | Doe | 2020-10-12 | Tech |
| 8473 | John | Patel | 2020-08-11 | Tech |
Answer:
This query filters the columns in the employees' table, where the department is 'Tech'. It further applies the LIKE clause to filter employees whose names start with 'J'. The AND operator is used to combine these conditions. Finally, the EXTRACT function is used to filter employees hired in the year 2020. The '%' character allows for any number of characters (including zero) to follow the initial 'J' in the name.
Hesai Technology SQL Interview Tips
Assuming that you've already got basic SQL skills, the next best tip we have to prepare for the Hesai Technology SQL interview is to solve as many practice SQL interview questions as you can!
Besides solving the above Hesai Technology SQL interview questions, you should also solve the 200+ DataLemur interview questions which come from companies like Microsoft, Google, Amazon, and tech startups.
Each DataLemur SQL question has multiple hints, full answers and most importantly, there's an interactive coding environment so you can easily right in the browser your SQL query and have it checked.
To prep for the Hesai Technology SQL interview you can also be a great idea to practice SQL problems from other tech companies like:
However, if your SQL coding skills are weak, forget about jumping right into solving questions – strengthen your SQL foundations with this interactive SQL tutorial.
This tutorial covers things like CASE/WHEN statements and GROUP BY – both of these pop up frequently in Hesai Technology interviews.
Hesai Group Data Science Interview Tips
What Do Hesai Technology Data Science Interviews Cover?
In addition to SQL interview questions, the other question categories to practice for the Hesai Technology Data Science Interview are:
- Probability & Statistics Questions
- Coding Questions in Python or R
- Product Analytics Questions
- Machine Learning Questions
- Behavioral Based Interview Questions
How To Prepare for Hesai Technology Data Science Interviews?
I'm sorta biased, but I think the best way to prepare for Hesai Technology Data Science interviews is to read my book Ace the Data Science Interview.
The book solves 201 data interview questions sourced from Microsoft, Amazon & startups. It also has a refresher covering Stats, ML, & Data Case Studies. 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.