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Top Advanced SQL Interview Questions and Answers

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SQL is a popular programming language for managing and organizing data in relational databases. If you are a software developer attending a technical interview, you will almost certainly be asked basic and advanced SQL interview questions at various stages of the interview. We've compiled this list of advanced SQL interview questions to help you prepare for your upcoming technical interview. Understanding the answers to these questions is essential for acing software engineering and programming interviews.

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Let’s go ahead and look at some advanced SQL interview questions and answers. We’ll also look at some FAQs to help you prepare for your upcoming SQL developer interview.

Here’s what we’ll discuss in this article:

  • Popular Advanced SQL Interview Questions and Answers
  • Additional Advanced SQL Interview Questions for Practice
  • FAQs on Advanced SQL Interview Questions

 Popular Advanced SQL Interview Questions and Answers

In this section, we’ll look at some popular advanced SQL interview questions and answers. We’ll also look at some additional practice SQL interview questions to help you prepare for your upcoming technical interview.

Q1. What do you understand about Indexes in SQL?

Indexes in SQL are used to help retrieve data smoothly and efficiently. There are three main types of indexes in SQL - Unique, Clustered, and Non-Clustered. In SQL, tables can have many non-clustered indexes but only one clustered index.

Q2. What do you do when data gets overloaded in your relational database?

If data is overloaded, you’re ideally required to apply a soft link. A soft link lets you store .idb and .frm files and retrieve them whenever necessary.

Q3. What do you understand about auto increment in SQL?

This is one of the most common advanced SQL interview questions asked in technical interviews. Auto Increment is a command through which a unique number is generated immediately when a new record is entered into a table.

Q4. Which command is used to select a unique entry or record in a table?

The command used to select a unique entry from the table is - “distinct.”

Q5. What are the two types of variables in SQL?

There are mainly two types of variables in SQL - Local and Global. Local variables are those that exist in a single function. Global variables exist in multiple functions and can be present throughout the program.

Q6. What do you understand by Recursive Stored Procedure?

The Recursive Stored Procedure is a common procedure through which developers can use the same code snippet multiple times in a program. Through this procedure, code snippets call themselves until a specific boundary condition is reached.

Q7. What is the main use of the NVL() function in SQL?

The NVL() function in SQL is essentially used to replace null entries with default values. If the first parameter has a null value, the function returns the next parameter. This is a function that is specific to Oracle databases.

Q8. What is the Unique Constraint in SQL?

The Unique Constraint in SQL ensures that every value in a particular record is unique. It prevents identical or similar values in a column from appearing in two different records.

Q9. What are some major differences between SQL and NoSQL?

This is a common SQL interview question asked in technical interviews. 

  • SQL is a language used to manage data in relational databases, whereas NoSQL applies to non-relational databases. 
  • SQL is a language used to store, manage and retrieve structured data, whereas NoSQL is used for unstructured data. 
  • NoSQL databases scale horizontally while SQL databases scale vertically.
  • SQL databases contain data in the form of tables, while NoSQL databases contain data in the form of documents, records, key-values, or graphs.

Q10. What do you understand about SQL Sandbox?

SQL Sandbox is an environment within the SQL databases where untested programs can be tested and run. There are primarily three types of SQL Sandboxes:

  • Sandbox for External Access
  • Safe Access Sandbox
  • Unsafe Access Sandbox

Additional Advanced SQL Interview Questions for Practice

In this section, we’ll look at some additional Advanced SQL interview questions that often appear in technical interviews. 

  1. Where is the MyISam table stored in the SQL database?
  2. What do you understand about Joins in SQL?
  3. What is the fundamental difference between CVarChar2 and Char datatype in SQL?
  4. What is the difference between Unique Key and Foreign Key in SQL?
  5. What do you understand about Data Integrity, and how do you ensure it in SQL?
  6. Explain the differences between the different types of Indexes in SQL
  7. Explain the process of Query Optimization in SQL
  8. What are the advantages of Normalization in SQL?
  9. What is the difference between Truncate and Drop commands in SQL?
  10. What do you understand about SQL Injection?
  11. What is a Trigger in SQL?
  12. Which are the different Operators that are available in SQL?
  13. What do you understand about SubQuery in SQL?
  14. What are Relationships in SQL? Which are the different types of Relationships in SQL?
  15. What do you understand about Clauses in SQL?
  16. Which are the ways by which Dynamic SQL can be deployed?
  17. Which are the different types of Set Operators available in SQL?
  18. What are Scalar and Aggregate functions in SQL?
  19. What are the advantages of Stored Procedures in SQL?
  20. What do you understand about Collation in SQL?

As a developer, your knowledge of SQL is extensively tested in technical interviews. These 30 advanced SQL interview questions will help you prepare for your upcoming software engineering interview. 

FAQs on Advanced SQL Interview Questions

Q1. What type of advanced SQL interview questions are asked in technical interviews?

Advanced SQL interview questions in technical interviews are fundamentally around core SQL concepts such as keys, parameters, functions, stored procedures, commands, and writing queries to manage, organize, and retrieve data from databases.

Q2. Is your knowledge of SQL tested in coding and design interviews at FAANG+ companies?

Your knowledge of SQL is primarily tested in systems design interviews at FAANG+ companies. Design interviews are a key part of the technical interview process.

Q3. What do you understand about SQL Limit?

The SQL Limit is a feature in SQL that limits the number of entries or records returned from a Query. This helps in the consistency and seamless retrieval of information from the database.

Q4. Which are the different types of user-defined functions in SQL?

There are three main types of user-defined functions in SQL - Inline Table-Valued Functions, Multi-Statement Valued Functions, and Scalar Functions.

Q5. What are your main responsibilities as an SQL developer?

As an SQL developer, you’re responsible for how data is managed and stored in relational databases. You’ll work closely with database administrators to ensure that the database is secure, responsive, and functions flawlessly.

Gear Up For Your Next SQL Interview

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