10 Juniper Networks SQL Interview Questions (Updated 2024)

Updated on

March 2, 2024

At Juniper Networks, SQL is used often for analyzing network configurations and traffic data. That's why Juniper Networks often tests SQL coding questions during interviews for Data Science, Data Engineering and Data Analytics jobs.

As such, to help you practice for the Juniper Networks SQL interview, we've collected 10 Juniper Networks SQL interview questions – able to answer them all?

10 Juniper Networks SQL Interview Questions

SQL Question 1: Identify Power Customers for Juniper Networks

Juniper Networks is a multinational corporation that develops and markets networking products. Its products include routers, switches, network management software, network security products and software-defined networking technology.

Assuming Juniper Networks has an e-commerce platform where customers can purchase products and given two tables (with , , , , ) and (with , , ), identify the top 5 customers who made the highest total order value in the past year.

The 'power customers' refer to the customers who contribute significantly to the company's revenue, i.e., users that have the highest total order value.

Example Input:
Example Input:
101John Doe2020-12-15
102Jane Doe2021-01-20


The following SQL query will get you the desired result. Note that this query uses the function to calculate the total order value for each customer, to group the results by customer, and together with to get the top 5 'power customers'.

The output of this query will show the top 5 customers (users' IDs and names) who made the highest total order value in the past year.

To practice a similar power-user data analysis problem question on DataLemur's free interactive SQL code editor, try this recently asked Microsoft SQL interview question: Microsoft SQL Interview Question: Teams Super User

SQL Question 2: Ranking Juniper Network Engineers Based on Success of Problem Resolution

Juniper Networks is a multinational corporation producing various networking products. You work as a Data Analyst in the company, and your task is to analyze the efficiency of network engineers in resolving networking issues. The table contains information about the engineers, problem tickets they handled, the date they resolved the issue, and the customer's satisfaction score after the problem was resolved.

Your task is to:

  1. Rank the engineers based on their average customer satisfaction score in each month.
  2. Particularly, for the month of May 2022, list out the top 3 engineers with the best average customer satisfaction score.
Example Input:
Example Output May 2022:


This query will give you the top 3 engineers with the highest average customer satisfaction score in May 2022. First, we use the window function to calculate the average satisfaction score and ranking for each engineer in each month. Then, we filter out the data of May 2022 and only select the top 3 engineers based on their ranking.

p.s. Window functions show up super often during SQL interviews, so practice the 27+ window function questions on DataLemur

DataLemur Window Function SQL Questions

SQL Question 3: What are the different normal forms (NF)?

Normalization is the process of organizing fields and tables of a database to minimize redundancy and dependency. While there are technically 5 levels (normal forms), the 3 most important normal forms you need to know about for SQL interviews at Juniper Networks are:

  1. First Normal Form (1NF): This should fix remove a table's duplicate columns. Also, each column should contain only a single value (no lists or containers of data), and finally each row of table should have a unique identifier as well.
  2. Second Normal Form (2NF): A table is in its second normal form if it meets all requirements of the first normal form and places the subsets of columns in separate tables. The relationships between tables are created using primary/foreign keys.
  3. Third Normal Form (3NF): The table should be in the second normal form. There should be no dependency on another non-key attribute (meaning a primary key should be the only thing required to identify the row).

Juniper Networks SQL Interview Questions

SQL Question 4: Optimize Product Inventory Management

Juniper Networks, a multinational corporation that develops and markets networking products, needs an efficient system for managing its product inventory. They are interested in knowing the stocks of their product parts in each warehouse, which city these warehouses are located in, and if the stocks are below the safety level. This will help them to streamline their supply chain, reduce operational costs, and improve customer satisfaction.

Example Input:
1"Router X"15
2"Switch Y"20
3"Server Z"10
Example Input:
Example Input:

Write a SQL query to list the parts that are below their safety stock level in each warehouse, including the name of the product, the warehouse city, and the current stock quantity.


This query joins the "product_parts", "warehouse", and "inventory" tables based on their respective keys. The WHERE clause filters out the parts that are below their safety stock level in each warehouse. With the output, the inventory managers can readily identify the products that need replenishing and in which city's warehouse.

SQL Question 5: Can you explain the meaning of database denormalization?

Denormalization is the practice of altering a database schema in a way that breaks the normalization rules (1st, 2nd, 3rd normal forms).

Denormalization is done to improve the performance of the database when it is being used for online analytics processing (OLAP), rather than online transaction processing (OLTP) use cases.

For these OLAP use cases, you're bottleneck frequently is joining multiple tables, but de-normalizing your database cuts these outs.

Denormalization can improve query performance by reducing the number of expensive joins required to retrieve data, but it comes with its own drawbacks too. By adding redundant columns, you incur more data storage costs, and there's need for more complex update and delete operations in order to maintain data integrity across all the duplicated data. Thus, it's important to carefully consider the trade-offs involved before implementing denormalization.

SQL Question 6: Click-through to Cart Conversion Rates for Juniper Networks

Given two tables- and , write a SQL query to find out the clickthrough conversion rate for Juniper Networks' digital products from viewing a product to adding a product to the cart for the month of March 2023. Assume you are given the number of clicks per product that led to the view of the product, and the number of clicks on the view that led to the product being added to the cart.

Example Input:

Example Input:

The output should have the product ID, total views, total carts, and click-through-conversion rates for the month of March 2023.


This SQL query joins the and tables on the . It then uses the function to total the views and the carts for each product and calculates the click-through-conversion rate. It finally filters the data to consider only the month of March 2023.

To practice a related SQL problem on DataLemur's free interactive coding environment, try this Facebook SQL Interview question: Meta SQL interview question

SQL Question 7: Can you explain the difference between a foreign and primary key in a database?

To explain the difference between a primary key and foreign key, let's start with some data from Juniper Networks's marketing analytics database which stores data from Google Ads campaigns:


+------------+------------+------------+------------+ | ad_id | campaign_id| keyword | click_count| +------------+------------+------------+------------+ | 1 | 100 | Juniper Networks pricing | 10 | | 2 | 100 | Juniper Networks reviews | 15 | | 3 | 101 | Juniper Networks alternatives | 7 | | 4 | 101 | buy Juniper Networks | 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 8: Find the maximum, minimum, and average price for each product category sold by Juniper Networks

Juniper Networks is a multinational corporation that sells various networking products. In your role as a data analyst at the company, you've been asked to create a SQL query which will calculate the maximum, minimum, and average prices of products sold in each product category.

Here are some sample tables:

table example:
table example:

Your SQL query should return a table that looks like this:

Expected Output:


This SQL query groups the data by product category. The aggregate functions MAX, MIN, and AVG find the highest, lowest, and average prices of the products in each group, respectively.

SQL Question 9: Calculating the Power Current based on Voltage and Resistance in Networks

Given a table in Juniper Networks that keeps track of various networks and their related voltage and resistance. A record is entered into this table every time the voltage or resistance changes. Also, given that power (in Watts) can be calculated using the formula .

Write a SQL query that calculates the power used by each network at the time of the latest voltage change and rounds the power to the nearest integer. Also, calculate the absolute difference in power between the latest and previous voltage change for each network.

Example Input:
145'Network A'105'2022-01-01 00:00:00'
245'Network A'204'2022-02-07 00:00:00'
345'Network A'303'2022-03-05 02:00:00'
467'Network B'408'2022-01-02 03:04:00'
567'Network B'306'2022-02-06 05:00:00'
689'Network C'5010'2022-01-03 06:00:00'
Example Output:
45'Network A'300200
67'Network B'150250
89'Network C'250null


Here we first calculate power for each record and get the previous power using the function in the CTE. Then in the CTE, we find the time of the latest record for each network. Finally, we join these two CTEs to get the power at the time of the latest record and the absolute change in power.

To practice a very similar question try this interactive Amazon Server Utilization Time Question which is similar for calculating total usage using data and this Microsoft Teams Power Users Question which is similar for finding top users based on their activity.

SQL Question 10: What's denormalization, and when does it make sense to do it?

Denormalization is the practice of altering a database schema in a way that breaks the normalization rules (1st, 2nd, 3rd normal forms).

Here's 3 reasons to de-normalize a database at Juniper Networks:

  1. Improved performance: Denormalization can often improve performance by reducing the number of expensive join operations required to retrieve data. This is particularly useful when the database is being used for online analytical processing (OLAP) as frequent joins across multiple tables can be slow and costly.

  2. Scalability: Denormalization can increase the scalability of a database by requiring less data to be read and processed when executing a query. This can be beneficial when the database is expected to handle a high volume of queries.

  3. Simplification: One way to simplify the design of a database is by using denormalization to reduce the number of tables and relationships that need to be managed. This can make the database easier to understand and maintain.

How To Prepare for the Juniper Networks SQL Interview

The key to acing a Juniper Networks SQL interview is to practice, practice, and then practice some more! In addition to solving the earlier Juniper Networks SQL interview questions, you should also solve the 200+ SQL questions on DataLemur which come from companies like Netflix, Airbnb, and Amazon. DataLemur Questions

Each exercise has multiple hints, full answers and best of all, there is an interactive coding environment so you can instantly run your SQL query answer and have it graded.

To prep for the Juniper Networks SQL interview it is also helpful to solve interview questions from other tech companies like:

But if your SQL coding skills are weak, forget about diving straight into solving questions – strengthen your SQL foundations with this free SQL for Data Analytics course.

SQL interview tutorial

This tutorial covers SQL concepts such as handling strings and creating summary stats with GROUP BY – both of these come up often during SQL job interviews at Juniper Networks.

Juniper Networks Data Science Interview Tips

What Do Juniper Networks Data Science Interviews Cover?

Besides SQL interview questions, the other types of questions covered in the Juniper Networks Data Science Interview are:

Juniper Networks Data Scientist

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