30 SQL Queries for Interview Questions and Answers in 2023

Welcome to this SQL query tutorial! As we know, to handle data, we use a very powerful language – Structured Query Language (SQL). In this blog, we will provide 30 SQL queries for interview questions with detailed explanations. 

In today’s market, SQL is in very high demand; especially in the IT industry. Our queries cover various scenarios and concepts. From data retrieval to table manipulation, we explore different topics. 

Detailed explanations break down query syntax and logic. Master SQL for interviews and real-world data tasks. Let’s start the journey to SQL mastery!

What is SQL?

Before going through the SQL queries, let’s first quickly see what SQL is. 

SQL full form is Structured Query Language. It is a data handling language that we use in Relational Database Management Systems (RDBMS ). SQL is used to conduct activities such as data updating, record adding, and record deletion in a database.

As a declarative language, SQL tells the database what you want & it will find out how to do it. This distinguishes it from procedural languages.

SQL’s popularity is widespread, with many companies and organizations utilizing it. It is a versatile language, applicable to various tasks. Overall, SQL provides a powerful means to interact with databases, enabling efficient data management and manipulation.

Now that we have a basic idea of what SQL is, let’s go through the queries frequently asked in interviews. 

Table: Employees

This is a database of a company with dummy employee’s data. Take a look at this table. With the help of this table, we will understand each SQL query one by one. 

SQL Queries for interview questions 

We will discuss about 30 frequently asked SQL queries for interview questions. The following is the list of queries.

First Level

• Q1: Retrieve all data from the Employees table
• Q2: Retrieve names of all employees
• Q3: Retrieve specific columns for employees in the HR department
• Q4: Retrieve all data from the Employees table sorted by salary in descending order
• Q5: Calculate the average salary of all employees
• Q6: Count the total number of rows in the Employees table
• Q7: Retrieve the maximum salary from the Employees table
• Q8: Retrieve the minimum salary from the Employees table
• Q9: Calculate the total sum of all salaries in the Employees table
• Q10: Retrieve unique departments from the Employees table

Second Level

• Q11: Retrieve employees with a salary higher than 55000
• Q12: Retrieve employees whose names start with the letter ‘J’
• Q13: Retrieve employees from the HR or Finance departments
• Q14: Retrieve employees with a salary between 50000 and 60000
• Q15: Retrieve names and salaries of the top 3 employees in the Marketing department
• Q16: Calculate the average salary of employees in the IT department
• Q17: Count the number of distinct departments in the Employees table
• Q18: Retrieve names of employees along with the length of their names
• Q19: Retrieve the first three characters of the names of all employees
• Q20: Concatenate the Name and Department columns and rename the result as EmployeeInfo

Third Level

• Q21: Retrieve employee(s) with the highest salary from the Employees table
• Q22: Retrieve names and salaries of employees with a salary higher than the average salary of all employees
• Q23: Retrieve names and salaries of employees with a salary higher than all HR department employees
• Q24: Retrieve names and salaries of employees with a salary equal to at least one Finance department employee
• Q25: Retrieve names and salaries of employees within a range of +/- 1000 from the average salary of all employees
• Q26: Count the number of employees in each department
• Q27: Calculate the average salary in each department
• Q28: Retrieve departments with more than 2 employees and display the department name along with the count of employees
• Q29: Insert a new employee record into the Employees table
• Q30: Update salaries of all employees in the Marketing department by adding 5000

Let’s see the SQL queries for interview questions and answers one-by-one.

Retrieve all data from the Employees table

Explanation: This query retrieves all columns and all rows from the Employees table.

Retrieve names of all employees

Explanation: This query retrieves the names of all employees from the Employees table.

Retrieve specific columns for employees in the HR department

Explanation: This query retrieves the ID, Name, and Salary of employees who work in the HR department.

Retrieve all data from the Employees table sorted by salary in descending order

Explanation: This query retrieves all columns and all rows from the Employees table, sorted in descending order of salary.

Calculate the average salary of all employees

Explanation: This query calculates the average salary of all employees in the Employees table.

Count the total number of rows in the Employees table

Explanation: This query counts the total number of rows in the Employees table.

Retrieve the maximum salary from the Employees table

Explanation: This query retrieves the maximum salary from the Employees table.

Retrieve the minimum salary from the Employees table

Explanation: This query retrieves the minimum salary from the Employees table.

Calculate the total sum of all salaries in the Employees table

Explanation: This query calculates the total sum of all salaries in the Employees table.

Retrieve unique departments from the Employees table

Explanation: This query retrieves all unique departments from the Employees table.

Retrieve employees with a salary higher than 55000

Explanation: This query retrieves all employees from the Employees table whose salary is greater than 55000.

Retrieve employees whose names start with the letter ‘J’

Explanation: This query retrieves all employees from the Employees table whose name starts with the letter ‘J’.

Retrieve employees from the HR or Finance departments

Explanation: This query retrieves all employees from the Employees table who work in the HR or Finance departments.

Retrieve employees with a salary between 50000 and 60000

Explanation: This query retrieves all employees from the Employees table whose salary is between 50000 and 60000.

Retrieve names and salaries of the top 3 employees in the Marketing department

Explanation:- This query will retrieve the names and salaries of the top 3 employees in the Marketing department, sorted in descending order of salary.

Calculate the average salary of employees in the IT department

Explanation: This query calculates the average salary of employees in the IT department.

Count the number of distinct departments in the Employees table

Explanation: This query counts the number of distinct departments in the Employees table.

Retrieve names of employees along with the length of their names

Explanation:– This query will retrieve the names of all employees along with the length of their names.

Retrieve the first three characters of the names of all employees

Explanation: This query retrieves the first three characters of the names of all employees.

Concatenate the Name and Department columns and rename the result as EmployeeInfo

Explanation: This query concatenates the Name and Department columns and renames the result as EmployeeInfo.

Retrieve employee(s) with the highest salary from the Employees table

Explanation: This query retrieves the employee(s) with the highest salary from the Employees table.

Retrieve names and salaries of employees with a salary higher than the average salary of all employees

Explanation:- This query will retrieve the names and salaries of employees whose salary is higher than the average salary of all employees.

Retrieve names and salaries of employees with a salary higher than all HR department employees

Explanation:- This query will retrieve the names and salaries of employees whose salary is higher than the salary of all HR department employees.

Retrieve names and salaries of employees with a salary equal to at least one Finance department employee

Explanation: This query retrieves the names and salaries of employees whose salary is equal to the salary of at least one Finance department employee.

Retrieve names and salaries of employees within a range of +/- 1000 from the average salary of all employees

Explanation: This query retrieves the names and salaries of employees whose salary is within a range of +/- 1000 of the average salary of all employees.

Count the number of employees in each department

Explanation: This query counts the number of employees in each department.

Calculate the average salary in each department

Explanation: This query calculates the average salary in each department.

Retrieve departments with more than 2 employees and display the department name along with the count of employees

Explanation: This query retrieves departments with more than 2 employees and displays the department name along with the count of employees.

Insert a new employee record into the Employees table

Explanation: This query inserts a new employee record into the Employees table with the specified Name, Department, and Salary.

Update salaries of all employees in the Marketing department by adding 5000

Explanation: This query updates the salaries of all employees in the Marketing department by adding 5000 to their current salary.

Conclusion

In conclusion, this article provides 30 SQL queries for interview questions with explanations for interview preparation or enhancing SQL skills. Mastering SQL is crucial for data management and offers IT career opportunities.

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Embark on your SQL learning journey with Technogeeks. Visit their website for course details and take the first step toward SQL mastery. Good luck!