# 11 VIZIO SQL Interview Questions (Updated 2024)

Updated on

June 23, 2024

VIZIO employees write SQL queries all the damn time for analyzing customer television viewing data and managing product inventory databases. So, it shouldn't surprise you that VIZIO almost always asks SQL problems during interviews for Data Science, Analytics, and & Data Engineering jobs.

Thus, to help prep you for the VIZIO SQL interview, we've curated 11 VIZIO SQL interview questions can you solve them?

## 11 VIZIO SQL Interview Questions

### SQL Question 1: Calculation of Month Wise Average Ratings

For this question, imagine the following scenario associated with the VIZIO dataset:

You are given a table named 'reviews' which contains customer reviews on various VIZIO products. The data includes a timestamp for when the review was submitted. You are requested to write a SQL query using Window Functions to calculate the average ratings (stars) for each product on a month-to-month basis.

Here's the sample input and output:

##### Example Input:
review_iduser_idsubmit_dateproduct_idstars
61711232022-06-08500014
78022652022-06-10698524
52933622022-06-18500013
63521922022-07-26698523
45179812022-07-05698522
##### Example Output:
mthproductavg_stars
6500013.50
6698524.00
7698522.50

With PostgreSQL, you can easily extract the month from a date using the EXTRACT function, and then use the AVG() function to find the average ratings within each month.

Here's a sample SQL query for this problem:

The above SQL query will partition the data by 'product_id' and 'month' and computes the average rating for each group. As a result, it will give you the average ratings for each product on a month-to-month basis. Keep in mind that EXTRACT function is being used to extract the month from the 'submit_date' and AVG is used to calculate average in each partition.

Pro Tip: Window functions are a popular SQL interview topic, so practice every window function problem on DataLemur

### SQL Question 2: Department Salaries

You're given a table of VIZIO employee and department salary information. Write a SQL query to find departments where the departments average salary is higher than the company's average salary.

Code your solution to this interview question and run your code right in DataLemur's online SQL environment:

The answer is LONG – 30+ lines of SQL. You can find a step-by-step solution with hints here: Department Salaries.

### SQL Question 3: What does the function do, and when would you use it?

The function can take in multiple paramaters, and returns the first input paramater that is not null. If all arguments are null, the COALESCE function will return null too.

Suppose you have a table of VIZIO salespeople and the number of deals they closed. If a salesperson didn't close any deals, the data from the 3rd-party CRM system exports a NULL value.

sales_personclosed_deals
Jason WrightNULL
Drew Jackson3
Chris HoNULL
Samantha Perez4

To change these NULLs to zeros, you can use the function in the following way:

This would result in the following data:

sales_personclosed_deals
Jason Wright0
Drew Jackson3
Chris Ho0
Samantha Perez4

### SQL Question 4: VIZIO's Products Sale Tracking

Given that you are a data analyst at VIZIO, the company wants to keep track of the sales of products across different regions. They are particularly interested in finding out how many units of each product are sold each month in each region. Can you design a database to help VIZIO solve this problem and also write a PostgreSQL query to determine the monthly sales for each product in each region?

##### Example Input:
product_idproduct_nameprice
50001VIZIO TV500
69852VIZIO Sound Bar200
12471VIZIO Smartcast100
##### Example Input:
region_idregion_name
10North America
20Europe
30Asia
##### Example Input:
sale_idproduct_idregion_idquantitysale_date
425150001105006/10/2022
189750001203006/15/2022
983612471304006/20/2022
420569852102507/12/2022
569812471306507/22/2022

This query calculates the total units sold for each product in each region for each month. It simply groups by the , and , and sums up the for each group. The result is ordered by and the total units sold in descending order by regions and products.

### SQL Question 5: In SQL, Are NULL values the same as a zero or blank space?

{#Question-5}

NULLs are NOT the same as zero or blank spaces in SQL. NULLs are used to represent a missing value or the abscence of a value, whereas zero and blank space are legitimate values.

It's important to handle NULLs carefully, because they can mess up your analysis very easily. For example, if you compare a NULL value using the = operator, the result will always be NULL (because just like Drake, nothing be dared compared to NULL). That's why many data analysis in SQL start with removing NULLs using the function.

### SQL Question 6: Filter VIZIO's Customers Based on Their Subscription and Purchase History

As an analytics professional working for VIZIO, you want to find all the customers who have both a VIZIO Smart TV and an active subscription to VIZIO's premium service. Furthermore, to better engage with loyal customers, you want to identify those who purchased their TV within the last two years.

##### Example Input:
101John Smith2019-03-232021-03-23
204Jane Doe2020-05-052020-06-05
354Aaron Johnson2021-09-082022-09-08
412Emma Brown2018-08-15NULL
575Michael Choi2022-01-152022-02-15
##### Example Output:
customer_idname
204Jane Doe
354Aaron Johnson
575Michael Choi

This SQL query filters out the customers from the database who have both a VIZIO Smart TV (purchased within the last two years) and an active subscription to VIZIO's premium service. The clause serves as the condition to filter the data. It first checks if the is within the last two years by subtracting '2 years' from the current date. Then it uses the clause to combine another condition, i.e., the should not be NULL representing an active subscription. The SELECT statement only retrieves the and of the customers meeting these conditions.

### SQL Question 7: How is the constraint used in a database?

A is like a secret code that unlocks the door to another table. It's a field in one table that points to the (the master key) in another table. This helps keep the data in your database organized and tidy, because it won't let you add new rows to the table unless they have the correct secret code (a corresponding entry in the table).

It's also like a special bond between the two tables - if you try to delete the data, the will be like "Whoa, hold on! I still need that information!" and prevent the deletion from happening.

### SQL Question 8: Calculate Average Screen Size of VIZIO Televisions Sold

You are a Data Analyst at VIZIO and you have been tasked to analyze the trend of televisions sold by VIZIO. More specifically, your task is to find out the average screen size of VIZIO televisions sold each month.

Consider the given tables, and .

##### Example Input:
sale_iddatemodel_idcustomer_id
10102/01/2021 00:00VZ508475
20104/15/2021 00:00VZ654849
30105/20/2021 00:00VZ608649
40105/22/2021 00:00VZ655647
50106/30/2021 00:00VZ504849
##### Example Input:
model_idscreen_size
VZ5050
VZ6060
VZ6565
VZ7070
VZ8080

Here is SQL query to get the average screen size of the VIZIO television sold each month.

This query first joins the sales and tv_models tables on the column. Then it calculates the average screen size of the VIZIO televisions sold each month. The result is a list of months together with the corresponding average screen size of the televisions sold. The list is ordered by month in ascending order.

To practice a very similar question try this interactive Wayfair Y-on-Y Growth Rate Question which is similar for calculating monthly metrics or this Amazon Average Review Ratings Question which is similar for finding average metrics.

### SQL Question 9: Calculate Click-Through-Rate for VIZIO Ads

VIZIO may want to analyze the efficiency of promotional campaigns they run for their TV sets. Suppose that they are tracking every single advertisement click and store the related information in a table. Additionally, if a click is followed by a purchase transaction, they store this info in a table. The company would like to calculate the click-through rate (CTR) for each TV model they are marketing for a certain month. The CTR is calculated as the total transactions divided by the total clicks, multiplied by 100 for a certain TV model.

Below are the and tables:

##### Example Input:
click_iduser_idclick_dateproduct_id
10134506/08/2022 00:00:006001
10225606/10/2022 00:00:006001
10332506/18/2022 00:00:007001
10443207/26/2022 00:00:007001
10512107/05/2022 00:00:007001
##### Example Input:
transaction_iduser_idtransaction_dateproduct_id
20134506/08/2022 01:00:006001
20225606/10/2022 01:30:006001
20332507/20/2022 14:00:007001
20443207/26/2022 16:10:007001

Note: We assume that transactions happen after clicks. So, for clarity, a transaction time is always later than the click time correspondingly.

Your task is to write a SQL query to calculate the CTR for each product for the month of June.

Here is one way to approach this using PostgreSQL:

This query first creates two sub-tables: one for the total clicks in June and one for the total transactions in June for each product. It then joins these two tables and calculates the CTR for each product. If there are no transactions for a product, it will return a CTR of 0.

To practice another question about calculating rates, try this SQL interview question from TikTok on DataLemur's interactive SQL code editor:

### SQL Question 10: Why is normalizing a database helpful?

Database normalization has several benefits:

• Reduces Redundancy: Normalization can minimize redundancy by breaking down a larger, general table into smaller, more granular tables. This often reduces the amount of data that needs to be accessed for particular queries, since some duplicated columns can be removed.

• Improves Data Integrity: Normalization can help to ensure the integrity of the data by minimizing the risk of data inconsistencies and errors. By establishing clear relationships between the tables via primary and foreign keys, and enforcing these constraints, you can have more reliable records and relationships stored in your DB.

• Improves Performance: Normalization can improve the performance of the database by reducing the amount of data that needs to be stored and accessed in a single table. This results in faster query times and better overall performance.

### SQL Question 11: Find Customers with 'Inc.' in their Name

As part of your task at Vizio, your manager asked you to filter the database for all customers whose name contains the word 'Inc.'. The customer records are stored in a table containing their unique ID and name. Write a SQL query to find these records.

##### Example Input:
customer_idcustomer_name
2003Vizio Inc.
5516Samsung Electronics
8619Sony Corporation
7523Apple Inc.
##### Example Output:
customer_idcustomer_name
2003Vizio Inc.
7523Apple Inc.

You can perform this query using the keyword in SQL.

In the provided SQL query, we retrieve the and from the table where the contains the string 'Inc.'. The percent sign (%) is a wildcard character in SQL that matches zero or more unspecified character(s), so it will return all the records where 'Inc.' is found anywhere in the customer name.

### VIZIO SQL Interview Tips

Assuming that you've already got basic SQL skills, the next best tip we have to prepare for the VIZIO SQL interview is to solve as many practice SQL interview questions as you can! Besides solving the above VIZIO SQL interview questions, you should also solve the 200+ SQL Interview Questions on DataLemur which come from companies like Facebook, Google and unicorn tech startups.

Each interview question has multiple hints, full answers and crucially, there's an interactive SQL code editor so you can instantly run your SQL query and have it executed.

To prep for the VIZIO SQL interview you can also be wise to practice SQL questions from other tech companies like:

In case your SQL coding skills are weak, forget about jumping right into solving questions – improve your SQL foundations with this DataLemur SQL tutorial.

This tutorial covers SQL concepts such as CASE/WHEN/ELSE statements and LEFT vs. RIGHT JOIN – both of which pop up routinely in SQL interviews at VIZIO.

### VIZIO Data Science Interview Tips

#### What Do VIZIO Data Science Interviews Cover?

Beyond writing SQL queries, the other types of questions to practice for the VIZIO Data Science Interview are:

#### How To Prepare for VIZIO Data Science Interviews?

I'm sorta biased, but I believe the best way to study for VIZIO Data Science interviews is to read my book Ace the Data Science Interview.

The book has 201 data interview questions sourced from Microsoft, Amazon & startups. It also has a crash course on Python, 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.