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Amazon, one of the most sought-after and renowned FAANG companies, has a spectrum of opportunities to offer. And like any other tech giant, Amazon also receives a huge amount of applications from around the globe. The journey to get past the competition and land a job at Amazon is challenging.
So, if you are a software engineer, a software developer, a data engineer, an engineering manager, or a tech lead gunning for a job at Amazon, then this article is for you! SQL is an important part of Amazon tech interviews and in this blog, we will explore some of the common Amazon SQL interview questions to help you prepare better.
Amazon Interview Process for Data Engineers <h2>
Amazon has an elaborate interview procedure similar to other FAANG companies. However, with the increasing seniority of the position, the interview process becomes more stringent and gruesome. The entire Amazon SQL interview process can be divided into three stages:
1. Phone Screen
After your profile is shortlisted, phone screening is the preliminary round of the interview process. The questions at the phone interview will be related to your resume and skills. This stage of the Amazon SQL interview process is more focused on understanding the applicant compared to their technical proficiency.
2. Technical Interview
Technical interview questions for Amazon are mostly related to coding, algorithms, and machine learning. You will be assigned 1 or 2 problems to solve within a stipulated amount of time.
If you are planning to apply for any of the data science positions or the positions of business analyst, business intelligence engineer, software engineer, software developer, and tech lead, then a technical interview on SQL will be a part of the process.
3. On-site Interview
The final and most challenging round of the Amazon SQL Interview process is the on-site interview, also known as “The Loop.” There can be 3-5 rounds, where each round goes on for about 45 minutes and is extremely exhausting.
The loop can be further broken down into 3 types of rounds:
1. Coding round: The primary focus of this round is to gauge an idea of the candidate's technical expertise. You will be assigned 1 or 2 coding problems, and your approach towards solving them will be analyzed.
2. Behavioral round: It is one of the integral rounds of all on-site interviews and is based on Amazon’s 14 leadership principles.
3. The Bar raiser round: This round is the final filter round. At the end of the round, only handpick candidates who pass the assessment of Amazon’s trained recruiters get selected.
Also read: How Hard Is It to Get a Job at Amazon?
Common SQL Interview Questions for Amazon
This section will serve as your “go-to SQL interview prep guide,” as we have covered the most commonly asked SQL interview questions at Amazon. In addition to getting well-versed in Amazon SQL interview questions, it is also suggested to brush up on your problem-solving skills, as it comes in handy during FAANG interviews.
1. How would you explain SQL to a person with no technical knowledge?
SQL stands for Structured Query Language. It is sort of like a tool that helps you communicate with a database. For example, imagine having a huge spreadsheet full of information, and you were trying to locate something in particular. You wouldn't find it by going through the hundreds of pages one by one; you would instead ask a question about the database to get back what you want.
It's like asking, "Give me all the orders from last week." SQL facilitates data retrieval or modification in a very fast and efficient manner even if the data becomes humongous. It is also easy to learn because its commands are similar to simple English.
2. What is the Amazon database?
Amazon database is one of the Amazon Web Services, which is a fully managed petabyte-scale data warehouse service. There are various Amazon Database Services available, such as DynamoDB, RDS, ElastiCache, and RedShift.
3. What is DynamoDB Auto Scaling?
DynamoDB Auto Scaling is a service feature that automatically scales read and write throughput for your DynamoDB tables based on traffic demands. In other words, if there is a change in the amount of data that needs to be read or written by your application, DynamoDB will automatically scale to meet that change without any manual intervention in the process. In this respect, it helps optimize your costs while ensuring performance through spikes in traffic.
4. Which of the four available AWS services will you choose from for collecting and processing e-commerce data for real-time analysis?
For collecting and processing E-Commerce data for real-time analysis, I’ll use DynamoDB. DynamoDB is a fully managed NoSQL database service that can be used for any type of unstructured data and can also be used for the data taken from e-commerce websites.
5. What is an Inner Join?
Inner join is the default join, which is used when no join is specified. INNER JOIN in SQL Inner Join returns the matched rows from both tables. It is the join operation that gets only those rows that satisfy the joins condition and discards the rows that do not match.
6. What is a full outer join in SQL?
The full outer join returns all the rows from both tables, inserting NULLs in places where no matching rows exist and matching up the rows where a match can be made. This join is useful if you want to retain all the data from both tables, whether they have corresponding values or not.
7. Which is the only constraint that works at the column level?
The only constraint that works at the column level is NOT NULL. A column cannot have a NULL (empty) value with this constraint, and this would be an important thing if the field always contains some data, like a primary key or mandatory fields like your e-mail or username.
8. After using the ALTER command, can a rollback be performed?
No, a rollback cannot be performed, as ALTER is a DDL command. A DDL command auto commits so once a DDL command is executed the changes become permanent in the database. Thus, there is no way to do a rollback.
9. What are some examples of pseudocolumns in SQL?
Pseudocolumns in SQL are columns that do not exist in the physical database but are there to be referenced like other columns. Examples include ROWNUM, which can give a unique number to every returned row from a query, and USER, which returns the name of the user currently logged into a database.
10. Write a command to change the password of the user x from "abcd" to "dfgh."
The SQL command to change the password of a user 'x' would be:
ALTER USER x IDENTIFIED BY dfgh
This updates the password to 'dfgh' for user 'x'.
11. What is a leader node and a computer node?
In Amazon Redshift, the leader node helps manage communication between the client applications and the data warehouse. It also manages how to assign tasks as well as execution plans for queries. The compute node executes these tasks, processes data, and returns results to the leader node. Therefore, a leader node ensures efficient interactivity between compute nodes and clients.
12. What is the difference between SQL and NoSQL?
Relational databases, like SQL organize the data into structured tables with defined relationships for increased data security and integrity. These are the databases that follow rigid schemas and work very well for structured data whose shape does not change much.
In contrast to SQL databases, NoSQL databases are non-relational and can process unstructured or semi-structured data like documents or graphs. NoSQL databases are designed to offer more flexibility, they can have schema changes on the fly and tend to perform better when it comes to dealing with larger, distributed data sets.
13. What is Amazon Redshift?
Amazon Redshift is a fully managed data warehouse service of AWS. Targeted towards big data processing, it allows users to perform a complex query on a huge amount of data with ease. With an MPP query engine at its core, it has the ability to distribute the queries across all nodes which gives significantly better performance. This makes it a great choice for organizations that have large datasets to analyze in real-time.
14. What is a stored procedure in SQL?
A stored procedure is a precompiled group of SQL statements and optionally control-of-flow statements stored in a database. You don't write and then execute one SQL statement, followed by another or else, but you can call that stored procedure, and they'll get executed all at once.
That improves performance because the SQL code inside the procedure has already been precompiled; hence its execution time is relatively shorter. Stored procedures are commonly used to perform procedures like data validation or complex queries.
15. What are SQL indexes, and why are they important?
SQL indexes are special look-up tables maintained by the database to speed up data retrieval. They do exactly what an index in a book does: they let the database quickly search for rows without having to scan the entire table.
Indexes enhance query performance, mostly in large databases, but they have trade-offs, such as increased storage and slower write operations since the index must be updated with every modification of the data.
Amazon SQL Interviews Questions for Practice
Irrespective of what your specialization is, tech interviews always feature some coding problems. We have uploaded numerous solved practice problems on our website for your reference. Here, we have mentioned a few important ones here for your reference:
- Write a program to find if a number or a string is a palindrome or not. (Solution)
- Implement a Min Stack that would support push, pop methods, and one method that returns the minimum element in the entire stack. (Solution)
- Check if the given binary tree is a binary search tree. (Solution)
Amazon SQL Queries Interviews Questions for Practice
Here are some SQL query questions to practice for the Amazon SQL interview. Practicing these questions will give you a better idea of different queries and how they can used in practical scenarios.
- Write a query to find the second-highest salary from an Employee table.
- Write a SQL query to retrieve all employees who earn a salary greater than the average salary in the company.
- Write an SQL query to get all the departments with more than 10 employees.
- Write a query to get employees who have joined the company in the last year.
- Write SQL for finding duplicate rows in the Sales table by considering one specific column, say CustomerID.
- Write a query to remove duplicate records from a table, yet keep one occurrence.
- Write a query to fetch all the products in the table Products that are not sold in the table Sales.
- Write a query to find all the employees from the table Employees who do not have a manager.
- Write a query to caluclate the aggregated revenue generated by each product from the table Sales.
- Write a query to fetch the top 3 customers based on total sales value from the table Orders.
Tips to Prepare for SQL Interview Questions at Amazon
A few pointers to remember while preparing for SQL interview questions are:
- Brush up on your basics! Getting your fundamentals strong would ensure a good start to your preparation.
- Get acquainted with the basic syntax, sub-queries, and queries of SQL.
- Expand your knowledge about Amazon, its services, and core values.
- Do not give up! The entire process might seem intimidating and exhausting, but the result is worth the struggle.
Nail Your Amazon SQL Interview With Interview Kickstart
Practicing numerous Amazon SQL interview questions will boost your confidence and improve your preparedness for the technical interview. With Interview Kickstart, you can fast track your interview prep with mock interviews, mentoring sessions, and interview prep material designed by FAANG+ experts.
Led by industry experts (from the likes of Google, Facebook, and LinkedIn), our instructors will help you build a strong foundation in various domains from data engineering and machine learning to Android and iOS development, and a lot more. Interview Kickstart will give you all the tools required to be successful in your career or land your dream job.
You can check out some of the success stories of our alumni who have advanced their careers with the help of Interview Kickstart.
FAQs About Amazon SQL Interview
Q1. What are the three stages of the Amazon SQL Interview?
The SQL interviews in Amazon are lengthy and require strenuous efforts. However, the SQL Amazon interview is unavoidable for all data engineers. The interview is divided into three rounds: preliminary phone interview, technical interview, and the loop.
Q2. Do I need to prepare for Amazon Leadership Principles for the Amazon interview?
Yes, as behavioral interviews form an integral part of Amazon’s recruitment process. The answer to the behavioral interview questions serves as the key to understanding your personality, social-interaction skills, and teamwork.
Q3. Does Amazon use SQL or NoSQL?
Amazon uses DynamoDB, a proprietary NoSQL database, along with Oracle and MySQL for specific purposes, ensuring scalability and performance in product information storage.
Q4. How many people pass the interview at Amazon?
The success rate, or the proportion of applicants who get a job offer after the Amazon Loop interview, is 20%, according to Misha Yurchenko, the author of "Cracking the Code."
Q5. What is the average Data Engineer salary at Amazon?
In the US, the average annual salary for an Amazon data engineer is around $135,00.
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