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SQL Developer Interview Questions with Answers and What to Expect!

Last Updated on:

23 November 2022
SQL Developer Interview Questions

The acronym SQL refers to the structured query language, which is a variety of domain-specific languages. With its assistance, the data that is kept in RDBMS systems can be communicated and manipulated. There are a vast number of subfields that are related to SQL, and each one has its own unique canon of ideas and principles. 

Before beginning a career in this field, one must be proficient in all aspects of SQL. In today's software market, there is a high demand for professionals who are able to think analytically and apply that thinking to SQL. This is due to the fact that SQL can play a wide variety of roles within a data-centric organization. Candidates who are energized by the prospect of working with data and the challenges it poses should give serious consideration to pursuing a career in SQL.

In general, databases store sets of information that may be retrieved and used in various contexts. A database management system is a set of tools for managing databases and the processes surrounding their creation and use.

What are the Job Responsibilities of an SQL Developer?

The daily routine of a SQL developer includes the creation of database management systems (DBMS), the development of application programming interfaces (API development), and the testing of code. Tasks such as designing tables and storing procedures, views, and functions are frequently performed during the development process.

SQL developers create working database prototypes to test system requirements by using input from project managers, business owners, analyst teams, and customers. In addition to documenting and reporting on the development of the code, they also perform code reviews and provide feedback to one another.

In most cases, the environments in which SQL developers do their work are ones that are calm and professional. Some people are able to work from other locations, such as their homes or other locations, by using the internet and email. Those who work with computers run the risk of experiencing a variety of injuries, including carpal tunnel syndrome, eyestrain, and sprains and strains in their necks and backs, despite the fact that accidents are relatively rare.

Their responsibilities also include the following:

  • Developing first-rate database applications.
  • Developing fresh queries.
  • Running some benchmarks on the SQL queries being used right now.
  • Expert use of T-SQL in creating and enforcing new functions and procedures.
  • Looking into the needs for regular business reporting and explaining what those needs are.
  • Digging and collecting data.
  • Creating relevant and useful documentation for the report.
  • Data migration requires the creation of scripts and processes.
  • Timely and regular reporting to management.
  • Problem-solving and improvising.

Job Requirements of an SQL Developer

An SQL developer is expected to have the following:

  • Bachelor's or master's degree in computer science or in any other relevant subject
  • Work experience as a SQL developer or in an equivalent position.
  • Competent in both JavaScript and HTML.
  • Knowledge of Transparent Data Encryption, SQL Server Reporting Services, and SQL Server Analysis Services is preferred (TDE).
  • Possess a deep understanding of Microsoft SQL Server and the T-SQL programming language.
  • A firm grasp of the practical uses and limitations of NoSQL and NewSQL database systems.

Nice to haves:

  • Superior ability to plan and organize one's time effectively and to think critically and creatively when faced with a challenge.
  • Excellent written and verbal communication skills.

The minimum education requirement for entry-level SQL developer positions is typically an associate's degree in computer information systems. General science, e-commerce, sysadmin, and DevOps are just some of the topics typically covered in a computer science degree program.

Standard SQL Developer Interview Questions

Here are some samples of questions you may encounter during an interview, along with their answers:

Question#1: What is RDBMS? Explain it in your way.

Expected Answer: The ability to create, modify, maintain, and connect with relational databases is made possible by a relational database management system (RDBMS), which is a collection of programs and tools for use by IT professionals. Table-based data is accessed using Structured Query Language (SQL) in the vast majority of commercialized RDBMS.

The relational database management system (RDBMS) is utilized by more companies than any other DBS. It provides a reliable method of archiving and accessing large datasets.

Relational database management systems (RDBMSs) are a specific kind of DBMS that keep records in a tabular, row-based format and use relationships between data rows to determine how the records should be accessed. The functions built into a relational database management system guarantee the safety, precision, integrity, and consistency of the information stored in it. A database management system uses a different kind of file storage than this.

Question#2: Can you explain schemas and their forms?

Expected Answer: A database's schema is a graphical diagram of its underlying data organization and logic. It creates and defines the connections between the various database entities. It is shorthand for the various restrictions that can be placed on a database. Also included a breakdown of the various data formats. You can also apply it to Views and Tables.

There is a wide range in the size and shape of schemas. Two of the most common are the star schema and the snowflake schema. The entity in a star schema takes on a star snowflake shape, while entities in a snowflake schema take on a snowflake form. So, schemas are the backbone of any database design.

Question#3: What are BLOB and Text in Databases?

Expected Answer: For binary data, we use BLOB or Binary Huge Objects, and for many strings, we use Text. Images, videos, audio files, and programs are just some of the types of binary data that BLOB can store.

BLOB values behave like byte strings because they lack a character set, just like bytes. As a result, comparison and sorting are crucial to understanding the numerical values of bytes.

Values of type Text act similarly to character strings and other non-binary types. The character set collection is indispensable for Text comparison and ordering.

Question#4: What is your understanding of denormalization?

Expected Answer: Using denormalization, you can get at information stored in a database with different data. Adding a second copy of a table's data aids database administrators in improving the overall system's performance. Combining database queries that merge information from several tables into a singular table causes data duplication in a table.

Question#5: What are entities?

Expected Answer: Entities are any observable real-world structures (i.e., people, data, or objects) for which a database can be created. Data for a specific entity type can be stored in a table. 

One type of database table used by financial institutions to store consumer data is the "consumer" table. To keep track of all of these details, each customer has their own list of characteristics and attributes (columns in the customer table).

Question#6: What are relationships?

Expected Answer: Connections between entities that share some kind of connection are said to have a relationship. Client names, bank details, and contact details (among other data) may all reside in the same database table. In addition, there may be relationships among the various tables.

Question#7: What is normalization?

Expected Answer: By arranging the tables and data of a database, normalization helps cut down on redundant and interdependent information. The process entails building tables and relating them to one another according to predefined rules. 

Following these guidelines, we can streamline normalization by removing unnecessary steps and ensuring that all dependencies are consistent.

Question#8: What do you understand by self-joins?

Expected Answer: Self-joins are a type of connection that can be used to join two tables together. This fact alone establishes the unary nature of the connection at hand. Each row in the table is joined to itself and all the other rows in the table using a self-join. 

To this end, a self-join is typically the go-to technique for comparing and assessing data within a single database table.

Question#9: How can you differentiate between OLAP and OLTP?

Expected Answer: OLTP, or online transaction processing, is a technique that facilitates real-time, massively parallel database transactions across distributed user groups. The term "database transaction" refers to any action taken on data stored in a database, including but not limited to updates, deletions, and queries.

The term "online" is used to differentiate between online transaction processing (OLTP) and online analytical processing (OLAP). Database updates can be made in real time with an OLTP system.

Question#10: Can you please explain your understanding of SQL injections?

Expected Answer: SQL injections are a kind of exploitation that make websites or apps vulnerable and prone to getting hacked.  Due to this flaw, hackers can access sensitive data contained in the website's or app's databases and even take over the site's or app's back-end activities. 

This technique allows an adversarial user to get access to a database by inserting malicious SQL statements into a database input field and then executing those statements. Gaining access to private information and performing database administration data via this means is extremely common. It achieves this by employing data-driven programs. SQL injection attack is another term for this kind of attack.

Here are some instances of SQL injection: 

  • Get around restrictions on accessing data in order to tweak a SQL query and get the desired results.
  • Information from several databases is targeted in a UNION attack.
  • In order to learn more about the database's database and version, you should look into it thoroughly.

The Present and Future of SQL Developers

SQL is an extremely important database system. In the future, SQL developers will be in demand in fields beyond IT, such as government, healthcare, retail, finance, and STEM. Every business needs a database to store its data. The benefits of pursuing a career in SQL are numerous. Some examples are as follows:

Proof that SQL will be around for a great many years: It ranked 2nd in a 2017 StackOverflow study of programming languages and frameworks, as shown in the accompanying bar chart.

Due to its open-source nature, SQL can be used and distributed without cost. After investing in your initial SQL certification training, you won't need to make any additional software or hardware purchases to continue honing your SQL skills. To carry out SQL, we make use of a XAMP/WAMP server, an open-sourced and free software package.

The time spent manually integrating data from multiple sources can be significantly reduced by using SQL to combine specific fields or the entire database.

When searched online, there are more than 25,000 job postings online specifically for SQL developers, indicating a high demand for those with relevant skills. An examination revealed that a considerable number of ads required applicants to understand and have SQL skills. 

The Structured Query Language (SQL) can be integrated with other programming languages, such as PHP and Java, depending on the queries.

Handle a mountain of information: Managing massive data of information presents significant challenges for conventional database management data. In this case, knowing SQL is useful. SQL has everything you need to manage massive amounts of data, whether you're dealing with a thousand or a million records.

It's a given that SQL will keep evolving for at least a couple or more decades, as the old phrase "Old is Gold" holds true in this case.

The Career Path of SQL Developers

Due to the increasing importance of data, SQL developers are in high demand. Taking on a career as a SQL developer can be highly rewarding. The route to getting there is often simply compared to other types of specialized work. There are many opportunities for you to advance professionally if you learn Microsoft SQL Server, as it is one of the top three RDBMS frameworks.

Programmers who work exclusively with SQL are typically either database experts or seasoned veterans of managing database development. While there are a number of different SQL dialects available, they all serve the same basic purposes (recovering, adding, modifying, and erasing database information).

SQL developers can also work as -

  • Azure/AWS ExpertDatabase Administrator (DBA)
  • Big Data Architect
  • Database Developer
  • Data Scientist
  • Data Analyst
  • Database Migration Engineer
  • Developer
  • Database Engineer
  • ETL Developer
  • NoSQL DBA
  • Reporting Engineer
  • SQL Server Writer

The Salary Range of an SQL Developer

An entry-level SQL developer can expect to make anywhere from 90 to 110k USD yearly, depending on where they work.


Josh Evan

Written by:

Josh Evan

Josh Evan is the professional career counselor and career development writer at When Work Works. He loves to see people from this field succeed through initiating the right thing in the right way. He never tells; he shows the way. We appointed John not because of his impressive CV. It was his counseling charisma which stood out of everything. He can implant idea, confidence and productive thoughts into mind almost effortlessly. His pen and mouth both speak for the greater good.


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