Top 20 SQL Query Interview Questions & Answers You Must Know!

If you're preparing for SQL query interview questions & answers in 2025, you can expect questions that test your ability to write efficient, optimized queries using advanced SQL techniques. Common SQL query interview questions & answers often focus on joins, subqueries, window functions, indexing, and performance tuning, all essential for handling large, normalized datasets in enterprise applications.

This blog covers the 20 most frequently asked SQL Query Interview Questions & Answers, curated for both freshers and experienced professionals.

Most Asked SQL Query Interview Questions & Answers for Freshers & Experts

Preparing SQL Query interview questions and answers sharpens your skills in complex data manipulation, crucial for machine learning pipelines. These queries test your command over relational database concepts and optimization. Mastery enables efficient data retrieval and processing, foundational for data-driven applications and AI model training.

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To help you prepare, here are some of the most commonly asked SQL query interview questions & answers that test fundamental and advanced concepts.

1. Write a query to get the EmpFname from the EmployeeInfo table in the upper case using the alias name as EmpName.

How to Answer:

When answering this question in SQL query interview questions & answers, explain that converting text to uppercase using SQL’s UPPER() function is useful for standardizing text formatting, especially in reporting or frontend displays. 

Mention that aliasing with AS improves clarity in result sets and aids in frontend data binding. Emphasize that this transformation happens at the database level, reducing the need for client-side processing.

Sample Answer:

To convert employee first names to uppercase, use the UPPER() function. Assign a meaningful alias using AS EmpName to make the output more readable and easier to work with. This approach ensures consistent formatting and simplifies integration with frontend frameworks like React or Bootstrap.

Example:

SELECT UPPER(EmpFname) AS EmpName FROM EmployeeInfo;

Output:

EmpName
--------
ROHAN
SUSHMITA
MANOJ

Output Explanation:

The query takes each EmpFname value, converts it to uppercase using UPPER(), and presents it under the alias EmpName. This standardizes the appearance of names without changing the original data in the database.

Use Case:

In a ReactJS-based employee directory, retrieving uppercase names directly from the SQL server ensures consistent name formatting across UI components. This reduces frontend logic, speeds up rendering, and simplifies data mapping when using frameworks like Bootstrap.

Also Read: Top 27 SQL Projects in 2025 With Source Code: For All Levels

2. Write a query to get the number of employees working in the department ‘HR’.

How to Answer:

To answer this question, explain that counting rows with specific criteria is a core SQL operation used in data analysis, reporting, and application logic. Use the COUNT(*) function with a WHERE clause to filter results based on the department. Highlight how this query supports efficient backend processing for real-time dashboards or admin panels.

Sample Answer:

To get the number of employees in the HR department, use the COUNT(*) function with a WHERE clause to filter rows where Department = 'HR'. This provides an efficient way to perform server-side aggregation and is ideal for integrating with real-time dashboards or admin tools.

Example:

SELECT COUNT(*) FROM EmployeeInfo WHERE Department = 'HR';

Output:

5

Output Explanation:

This query counts the number of rows in the EmployeeInfo table where the Department is ‘HR’. The result helps power admin dashboards and analytics without requiring additional frontend logic.

Use Case:

In a React.js admin dashboard, you can display the HR team size dynamically using a Bootstrap card component. This query allows the backend to handle the logic, reducing API payload and improving frontend performance for live metrics.

Also Read: Free SQL Certification Course Online [2025]

3. What query will you write to fetch the current date?

How to Answer:

When answering this question, explain that retrieving the current server date ensures consistent time tracking across applications. SQL provides built-in functions like SYSDATE() (MySQL database) and GETDATE() (SQL Server) to fetch the server’s current timestamp. This is vital for features like audit logging, scheduling, session management, and aligning backend processes with frontend time displays.

Sample Answer:

To fetch the current date and time from the database server, use the SYSDATE() function in MySQL. This ensures accurate, server-controlled timestamps, which are essential for syncing frontend components with backend logic in full-stack applications.

Example:

SELECT SYSDATE();

Output: 

2025-05-15 10:30:00

Output Explanation:

The query returns the current date and time based on the database server’s clock. This output is consistent and tamper-proof, making it ideal for tracking user actions, scheduling events, and validating time-sensitive operations.

Use Case:

In a React.js booking system, using server-side timestamps via SYSDATE() ensures accurate and secure time validation. This prevents manipulation on the client side and helps maintain transactional integrity throughout the application.

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4. Write a query to fetch only the place name(string before brackets) from the Address column of the EmployeeInfo table.

How to Answer:

Explain that extracting a portion of a string from a larger text field is a common data cleaning and preprocessing task in SQL. Use string functions like MID() (or SUBSTRING()) combined with LOCATE() to isolate the part of the string before the first occurrence of a specific character, such as an opening bracket. This improves data clarity and offloads formatting work from the frontend.

Sample Answer:

To fetch only the place name portion from the Address column, use the MID() function along with LOCATE() to extract the substring that appears before the first bracket (. This is especially useful when formatting addresses for UI display without exposing unnecessary details.

Example:

SELECT MID(Address, 1, LOCATE('(', Address) - 1) AS PlaceName FROM EmployeeInfo;

Note: In MySQL, MID() starts from index 1 (not 0).

Output:

PlaceName
---------------
123 Rajeev Chowk  
456 MG Road

Output Explanation:

The query extracts the characters in the Address column up to (but not including) the first opening bracket (. This results in clean place names, free of extra data like postal codes or region tags.

Use Case:

In a React.js location-based directory or map view, this query enables displaying clean, user-friendly location names in tooltips or listings. Performing this transformation in MySQL ensures consistent formatting across the app and reduces unnecessary string parsing in the frontend.

Also Read: SQL for Data Science: Functions, Queries, and Best Practices

5. Write a query to create a new table whose data and structure are copied from another table.

How to Answer:

Explain that duplicating a table, both its structure and contents, is essential for creating testing environments, backups, or staging areas. SQL provides CREATE TABLE AS SELECT to quickly clone a table, which helps developers safely run tests or develop new features without altering production data.

Sample Answer:

To duplicate the EmployeeInfo table along with its data, use the CREATE TABLE AS SELECT statement. This allows you to create a new table with identical columns and contents, which is useful for development, testing, or migration purposes.

Example:

CREATE TABLE NewTable AS SELECT * FROM EmployeeInfo;

Output:

NewTable created with structure and all data copied from EmployeeInfo.

Output Explanation:

This query creates a new table named NewTable that mirrors the schema and data of EmployeeInfo. It avoids the need to manually define column types, constraints, or import rows separately.

Use Case:

If you're building a new feature in a React.js front end and need to test schema changes, this query allows you to create a duplicate table for development safely. It’s especially useful in CI/CD pipelines or cloud-based environments (e.g., AWS, Azure) where schema versioning and non-destructive testing are critical.

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6. Write a query to display the names of employees that begin with ‘S’.

How to Answer:

Explain that SQL’s LIKE operator is used for pattern matching in string data. Prefix filtering, such as finding names that start with a specific letter, is a common requirement in search features and filtered views. Using LIKE 'S%' enables efficient string matching directly in the database layer, reducing the need for additional filtering on the frontend.

Sample Answer:

To find employees whose first names begin with the letter ‘S’, use the LIKE clause with the % wildcard. This query is useful for implementing search filters or user-specific views in full-stack applications.

Example:

SELECT * FROM EmployeeInfo WHERE EmpFname LIKE 'S%';

Output:

EmpID | EmpFname | EmpLname | Department | Address
-----------------------------------------------------
102   | Suleman  | Khan     | Sales      | Bandra (Mumbai)
115   | Sayan    | Ghosh    | Marketing  | Shyambazar (Kolkata)

Output Explanation:

The query returns all records from EmployeeInfo where the EmpFname field begins with the letter ‘S’. This filtering is done at the database level, which reduces processing time and memory usage on the client side.

Use Case:

This query supports fast server-side filtering for search inputs in a React.js application backed by a Python or .NET API. When deployed in a Docker or Kubernetes environment, such efficient queries help keep resource usage low while ensuring fast UI rendering.

Also Read: Top 10 Real-Time SQL Project Ideas: For Beginners & Advanced

7. Write a query to retrieve the top N records.

How to Answer:

Explain that SQL’s LIMIT (or TOP in SQL Server) is used to restrict the number of rows returned, which is useful for showing rankings, leaderboards, or summaries in analytics dashboards. This kind of query is efficient and reduces both backend load and frontend processing time, ideal for real-time applications. 

Sample Answer:

To get the top 3 highest-paid employees, use the ORDER BY clause to sort salaries in descending order, then apply LIMIT to return only the top 3 records. This is commonly used in dashboards, reports, and data-driven UI elements.

Example (MySQL):

SELECT * FROM EmployeePosition ORDER BY Salary DESC LIMIT 3;

Output:

EmpID | EmpPosition | Salary
-----------------------------
110   | Manager     | 120000
105   | Lead Dev    | 115000
102   | Senior Dev  | 110000

Output Explanation:

The query sorts employee records by Salary in descending order and returns only the top 3 entries. This approach is ideal when building components like salary rankings or performance charts.

Use Case:

When building a React.js dashboard for HR or leadership, this query helps populate top-earning employees in real time. By limiting the result set, you ensure better performance in microservice-based architectures, especially when deployed via Kubernetes or Dockerized APIs using Python or .NET for backend logic.

Also Read: Top 27 SQL Projects in 2025 With Source Code: For All Levels

8. Write a query to obtain relevant records from the EmployeeInfo table ordered by Department in ascending order and EmpLname in descending order.

How to Answer:

Explain that multi-level sorting is used to organize data in a meaningful order, often applied in admin dashboards and reports. SQL’s ORDER BY clause supports sorting by multiple columns in different directions, which is useful in applications where structured data presentation is key for readability and UX.

Sample Answer:

To sort by department in ascending order and employee last name in descending order, use the ORDER BY clause with specified sort directions. This is particularly effective in generating structured, user-friendly views in enterprise apps.

Example:

SELECT * FROM EmployeeInfo ORDER BY Department ASC, EmpLname DESC;

Output:

EmpID | EmpFname | EmpLname | Department | Address
---------------------------------------------------
101   | Rakesh   | Bhat     | HR         | H/10 Jain Nagar
110   | Sulekha  | Mishra   | HR         | 25 MG Road
105   | Sharan   | Chawla   | Sales      | 1B Uttam Vihar
107   | Vikas    | Singh    | Sales      | 17/8 CR Avenue

Output Explanation:

The result is first sorted by Department in ascending order (e.g., HR before Sales). Within each department group, the results are further sorted by EmpLname in descending order. This layered ordering improves the clarity of tabular data in both internal and customer-facing systems.

Use Case:

In a React.js dashboard powered by Python or C# APIs, this query provides pre-sorted data to UI tables, improving load performance and minimizing frontend computation. Especially in Dockerized backends orchestrated via Kubernetes, efficient sorting at the database level optimizes overall system responsiveness.

Also Read: SQL For Beginners: Essential Queries, Joins, Indexing & Optimization Tips

9. Write a query to get the details of employees whose EmpFname ends with ‘A’.

How to Answer:

Explain that suffix-based filtering helps refine search results, which is commonly used in user personalization, segmentation, and reporting features. The SQL LIKE operator is used with a % wildcard to match text patterns at the end of strings.

Sample Answer:

To filter records where the first name ends with the letter 'a', use the LIKE '%a' pattern. This returns all entries where the EmpFname column has names ending in 'a', which can be useful in marketing segmentation or dynamic UI rendering.

Example:

SELECT * FROM EmployeeInfo WHERE EmpFname LIKE '%a';

Output:

EmpID | EmpFname | EmpLname | Department | Address
---------------------------------------------------
103   | Kalpana  | Patel    | Finance    | 22 Hill St
118   | Sheya    | Sharma   | Marketing  | 34 Lake Rd

Output Explanation:

The query selects all employees whose first names conclude with the letter 'a'. This type of suffix matching is ideal for tailoring UI views, search filters, or user-specific features.

Use Case:

In a full-stack app with a C# or Python backend, this query can serve filtered datasets to React.js interfaces. By handling this filtering server-side (e.g., inside a Dockerized container managed by Kubernetes), you improve response times and offload unnecessary processing from the front end.

10. Create a query to fetch details of employees having “DELHI” as their address.

How to Answer:

Explain that prefix-based string filtering helps identify records from specific geographic regions. The LIKE operator with 'DELHI%' retrieves addresses that begin with the word "DELHI", useful in map-based visualizations, location filters, and data segmentation.

Sample Answer:

To find employees whose address starts with "DELHI", use the LIKE operator with 'DELHI%'. This enables backend systems to pre-filter data by location, improving UI performance and supporting geospatial features.

Example:

SELECT * FROM EmployeeInfo WHERE Address LIKE 'DELHI%';

Output:

EmpID | EmpFname | EmpLname | Department | Address
---------------------------------------------------
120   | Rajesh   | Kumar    | HR         | DELHI Sector 5
123   | Anjali   | Singh    | Sales      | DELHI Connaught Place

Output Explanation:

The query returns employees whose addresses begin with "DELHI". This structured filtering improves UI clarity for React.js map or table components and supports location-based backend analytics.

Use Case:

This query can power location-based dashboards in a React.js frontend, where backend services, possibly containerized with Docker and orchestrated by Kubernetes, serve clean, filtered data. It also integrates with Python-based ML models to perform geographic trend analysis or employee clustering based on region.

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11. Write a query to fetch all employees who also hold the managerial position.

How to Answer:

Explain that joining tables is a core SQL concept used to combine related data across normalized schemas. This is particularly useful in enterprise systems where React.js or Next.js frontends consume data from C#, Python, or C++ backend services. Performing joins server-side ensures efficient data structuring and reduces frontend complexity, especially in Dockerized environments managed by Kubernetes.

Sample Answer:

To retrieve employees with the role of 'Manager', an INNER JOIN is used to combine the EmployeeInfo and EmployeePosition tables using EmpID as the common key. The WHERE clause is used to filter only those records where the employee holds the 'Manager' position.

Example:

SELECT E.EmpFname, E.EmpLname, P.EmpPosition
FROM EmployeeInfo E
INNER JOIN EmployeePosition P ON E.EmpID = P.EmpID
WHERE P.EmpPosition = 'Manager';

Output:

EmpFname | EmpLname | EmpPosition
----------------------------------
Manoj    | Sharma   | Manager
Asif     | Khan     | Manager

Output Explanation:

This query performs an INNER JOIN on the EmployeeInfo and EmployeePosition tables via the EmpID field. It returns only those records where the EmpPosition is 'Manager'. This allows for seamless aggregation of user data across tables in normalized databases.

Use Case:

In full-stack applications, especially those using a Dockerized backend with services written in C# or Python, this query is useful for role-based data filtering. It can be used in RESTful APIs or GraphQL resolvers to supply React.js components with filtered data for dashboards, access control panels, or organizational charts. 

Performing this join at the database level ensures fast query performance and minimizes API response size, which is critical for scalable deployments managed by Kubernetes.

Also Read: Detailed SQL Syllabus Structure for Data Science Certification

12. Create a query to generate the first and last records from the EmployeeInfo table.

How to Answer:

Explain that retrieving boundary records using SQL’s MIN() and MAX() functions is essential for applications that require ordered navigation, such as auditing logs, pagination features, or identifying earliest/latest entries in time-series datasets. These techniques are commonly used in full-stack systems where backend services in Python, C#, or Java serve React.js or Next.js frontends.

Sample Answer:

To fetch the first and last records from a table, use scalar subqueries with MIN(EmpID) and MAX(EmpID) to identify the smallest and largest values of the primary key. This method is both efficient and scalable due to index utilization on primary key fields.

Example – Fetch First Record:

SELECT * FROM EmployeeInfo 
WHERE EmpID = (SELECT MIN(EmpID) FROM EmployeeInfo);

Example – Fetch Last Record:

SELECT * FROM EmployeeInfo 
WHERE EmpID = (SELECT MAX(EmpID) FROM EmployeeInfo);

Output:

First Record:

EmpID | EmpFname | EmpLname | Department | Address
---------------------------------------------------
101   | Akash    | Singh    | HR         | 17/3 SS Road

Last Record:

EmpID | EmpFname | EmpLname | Department | Address
---------------------------------------------------
150   | Priya    | Sharma   | Sales      | 78 Netaji Rd

Output Explanation:

These queries identify and return the rows where the EmpID matches the minimum and maximum values found in the table. This approach helps retrieve the earliest and latest records based on primary key ordering, which is commonly used in maintaining UI navigation, logs, and dataset boundaries.

Use Case:

In a React.js web application that includes paginated tables or audit trails, you can use these queries in the backend, built with Python, Java, or C#, to determine the first and last available records. This supports efficient client-side rendering, accurate pagination controls, and consistent data access across distributed systems hosted in Docker containers and orchestrated with Kubernetes.

Also Read: Is SQL Hard to Learn? Breaking Down the Challenges and Solutions

13. Create a query to check if the passed value to the query follows the EmployeeInfo and EmployeePosition tables’ date format.

How to Answer:

Explain that validating date formats is critical for preventing invalid data insertion and ensuring application stability. SQL’s ISDATE() function helps confirm whether a given string follows a recognizable date format. This is particularly useful in form submissions, ETL pipelines, and data ingestion processes in full-stack applications using Java, Python, or C# backends.

Sample Answer:

The ISDATE() function returns 1 if the input expression is a valid date format and 0 otherwise. It serves as a safeguard in backend validation layers, especially when handling date inputs from frontend forms or external APIs.

Example:

SELECT ISDATE('01/04/2020') AS "MM/DD/YY";

Output:

MM/DD/YY
---------
0

Output Explanation:

In this example, the query returns 0, indicating that the input string '01/04/2020' is not recognized as a valid date in the expected SQL Server format. This allows developers to catch and handle improperly formatted date strings before processing or storing them.

Use Case:

In a React.js application where users submit forms with date fields, your backend, written in Python, Java, or C#, can invoke this validation query to check for correct date formatting. This approach acts as a backend fallback for frontend validation, helping to avoid data corruption or processing errors. It's especially effective in containerized SQL Server deployments running within Docker and orchestrated by Kubernetes, where validation must be efficient and scalable.

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14. Create a query to obtain display employees having salaries equal to or greater than 150000.

How to Answer:

Explain that numeric filtering using SQL’s WHERE clause is crucial for payroll management, budgeting, and compensation benchmarking in enterprise applications. This enables backend APIs to provide filtered datasets to frontends like React.js and supports real-time analytics in scalable, containerized environments.

Sample Answer:

To retrieve employees with salaries equal to or above ₹150,000, use a conditional filter with the WHERE clause. This type of filtering is commonly used in payroll dashboards, HR analytics tools, and compliance systems.

Example:

SELECT EmpName FROM Employees WHERE Salary >= 150000;

Output:

EmpName
------------
Rajesh Kumar
Neha Sharma

Output Explanation:

This query selects employees whose salary is ₹150,000 or higher. In this case, Rajesh Kumar and Neha Sharma meet the criteria. Such filtered outputs support use cases like generating salary bands, identifying top earners, or calculating payroll taxes.

Use Case:

In an Indian enterprise HRMS system, a React.js frontend may allow users to filter employees by salary. A backend service, built in Python, Java, or C#, can run this query against a SQL database hosted in a Docker container. When orchestrated via Kubernetes, this ensures scalable delivery of high-earning employee data to payroll or analytics modules.

15. Write a query to fetch the year using a date.

How to Answer:

Explain that extracting the year component from a date is essential for generating time-based summaries, especially in financial, audit, and reporting modules common in Indian business systems. SQL’s YEAR() function enables precise temporal filtering for backend logic and frontend display.

Sample Answer:

To retrieve the current year from the database server’s system date, use the YEAR() function with GETDATE(). This is often used in dynamic reporting, filtering datasets, and generating year-wise statistics across domains such as finance and operations.

Example:

SELECT YEAR(GETDATE()) AS "Year";

Output:

Year
-----
2025

Output Explanation:

This query returns the current year (2025 in this case) from the system’s date and time. Such values are often used to build filters in reporting dashboards or determine financial year periods dynamically.

Use Case:

In full-stack applications, a Python or C# backend can use this query to fetch the current year and filter records accordingly (e.g., WHERE YEAR(InvoiceDate) = 2025). React.js frontends can then present annual reports, trends, or audits. When deployed inside Docker containers on Kubernetes, scalability and performance in data-intensive environments are ensured.

16. Create an SQL query to fetch EmpPostion and the total salary paid for each employee position.

How to Answer:

Explain that aggregating salary data by role is essential for budgeting, compensation benchmarking, and department-level financial analysis in Indian business systems. SQL’s SUM() function paired with GROUP BY allows efficient aggregation for both backend analytics and frontend visualization.

Sample Answer:

To calculate total salary per employee role, use the SUM() function along with GROUP BY EmpPosition. This group records by position and computes the cumulative salary for each role, enabling deeper financial insights and visual summaries.

Example:

SELECT EmpPosition, SUM(Salary) AS TotalSalary
FROM EmployeePosition
GROUP BY EmpPosition;

Output:

EmpPosition | TotalSalary
--------------------------
Manager     | 250000
Developer   | 340000
HR          | 150000

Output Explanation:

The query aggregates salary values for each unique employee position. This helps finance teams evaluate salary distribution across roles, supporting data-driven decisions on workforce planning.

Use Case:

In a containerized backend built with Python or Java, this query can be run to serve summarized salary data via REST or GraphQL APIs. React.js frontends can then use this aggregated data to render salary distribution charts. With Kubernetes managing the Dockerized infrastructure, the architecture ensures scalability and responsiveness even during high data loads or reporting cycles.

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17. Write a query to find duplicate records from a table.

How to Answer:

Start by explaining that detecting duplicates is crucial in enterprise systems for maintaining clean, reliable datasets. Using SQL’s GROUP BY with HAVING COUNT(*) > 1 allows backend systems to identify data anomalies proactively, which is critical in large Indian organizations managing HR, payroll, or compliance data.

Sample Answer:

To detect duplicate employee records, group by fields that should uniquely identify an employee—such as EmpID, EmpFname, and Department. The HAVING clause filters these groups to show only those with more than one occurrence, indicating duplication.

Example:

SELECT EmpID, EmpFname, Department, COUNT(*) AS RecordCount
FROM EmployeeInfo
GROUP BY EmpID, EmpFname, Department
HAVING COUNT(*) > 1;

Output:

EmpID | EmpFname | Department | RecordCount
-------------------------------------------
108   | Amit     | Sales      | 2
112   | Priya    | HR         | 3

Output Explanation:

The result reveals duplicate entries for employees like Amit and Priya. Such redundancy can cause inconsistencies in reporting, payroll, and access control. Identifying and removing duplicates is key to ensuring accuracy.

Use Case:

This query can be used for automated validation routines before populating dashboards in a microservices-based architecture where Python or C# services fetch HR data. Clean data ensures that React.js or Next.js interfaces display accurate, trustworthy information, boosting end-user confidence. When deployed in Docker containers orchestrated by Kubernetes, this validation step can be integrated into continuous data quality pipelines.

18. Create a query to fetch the third-highest salary from the EmpPosition table.

How to Answer:

Start by explaining that retrieving the nth highest value is essential for rank-based compensation analysis. In Indian enterprises, this helps HR teams analyze salary bands or benchmark pay grades. SQL nested queries make this possible even in systems that don’t support advanced ranking functions. It’s a valuable pattern in backend services that power frontend dashboards.

Sample Answer:

To fetch the third-highest salary, we use nested TOP clauses with ORDER BY. The inner query retrieves the top three salaries, and the outer query selects the lowest among them—effectively the third-highest overall.

Example (SQL Server):

SELECT TOP 1 Salary
FROM (
  SELECT TOP 3 Salary
  FROM EmployeePosition
  ORDER BY Salary DESC
) AS Temp
ORDER BY Salary ASC;

Output:

CopyEdit
Salary
-------
95000

Output Explanation:

The query returns ₹95,000, the third-highest salary in the EmployeePosition table. This approach is helpful when performing compensation analysis or setting salary thresholds in policy-driven organizations.

Use Case:

This logic is used in backend C# or Python services for salary analytics tools. When integrated into Dockerized microservices and orchestrated by Kubernetes, it enables responsive and scalable data access. React.js dashboards can use the result to display leaderboards, top-earner badges, or percentile bands, adding rich interactivity to enterprise HR software.

19. Write an SQL query to find even and odd records in the EmployeeInfo table.

How to Answer:

Begin by explaining that row classification using modulo operations is commonly used in frontend applications, especially for alternating row colors, enhancing data readability. SQL’s ROW_NUMBER() function, when combined with MOD(), enables even/odd row identification. This is useful in React.js tables styled with Bootstrap or Material UI and powered by efficient backend APIs.

Sample Answer:

To retrieve employee records in even-numbered row positions, we generate row numbers using the ROW_NUMBER() function, then apply the MOD() function to filter only even rows (MOD(rowno, 2) = 0).

Example:

SELECT EmpID FROM (
  SELECT ROW_NUMBER() OVER (ORDER BY EmpID) AS rowno, EmpID
  FROM EmployeeInfo
) AS T
WHERE MOD(rowno, 2) = 0;

Output:

EmpID
-----
102
104
106

Output Explanation:

This query selects only those employee records that fall on even-numbered positions in the result set (e.g., 2nd, 4th, 6th). This supports backend logic used to differentiate row formatting for visual consistency in frontend tables.

Use Case:

You can implement this in backend Python or Java microservices to segment data before sending it to a React.js or Next.js UI. The frontend can then apply alternating styles (e.g., striped rows) for better readability. When deployed in Docker containers orchestrated by Kubernetes, this method ensures a fast and scalable user experience in data-intensive enterprise dashboards.

20. Create a query to fetch the list of employees of the same department.

How to Answer:

Explain that self-joins are used to relate rows within the same table. They are valuable in organizational contexts, such as listing employees who work in the same department. This technique supports features like team visualizations in React.js frontends, powered by backend APIs written in Python, Java, or C#.

Sample Answer:

To retrieve employees who belong to the same department but exclude themselves from the match, we use a self-join on the EmployeeInfo table with a condition that matches departments and filters out identical employee IDs.

Example:

SELECT DISTINCT E.EmpID, E.EmpFname, E.Department
FROM EmployeeInfo E
JOIN EmployeeInfo E1 ON E.Department = E1.Department AND E.EmpID != E1.EmpID;

Output:

EmpID | EmpFname | Department
-----------------------------
105   | Sunita   | Marketing
109   | Rakesh   | Marketing
111   | Anil     | Finance
115   | Kavita   | Finance

Output Explanation:

The query returns employees who share the same department with at least one other person, excluding self-pairs. This allows for clean team views, ensuring employees aren't redundantly paired with themselves.

Use Case:

Use this query in Python or C# backend services to dynamically generate department-based team lists. These lists can then be rendered in React.js or Next.js organizational dashboards. When deployed via Docker containers and orchestrated with Kubernetes, this pattern scales well for large enterprises with distributed teams.

Let’s explore how to effectively explain SQL Query Interview Questions & Answers in your upcoming interview.

How to explain SQL query in an interview?

Explaining an SQL query in an interview requires clarity, technical precision, and a logical breakdown of the query components. You should demonstrate your understanding of the database schema, SQL syntax, and business context while highlighting how the query solves a problem efficiently. Emphasizing performance considerations and anticipating follow-up questions reflects advanced database knowledge crucial in real-world applications involving complex data systems.

• Context Introduction: Briefly describe the business scenario and the database or tables involved in setting the stage.
• Objective Clarification: Clearly state what the query aims to accomplish—data retrieval, update, aggregation, or filtering.
• Query Breakdown: Explain key SQL clauses—SELECT, FROM, JOIN, WHERE, GROUP BY, ORDER BY—and their roles in shaping results.
• Functions and Optimizations: Highlight SQL functions used (e.g., CASE, COALESCE, date functions) and mention indexing or optimization techniques.
• Output Summary and Impact: Summarize the query output and how it addresses the business problem, mentioning scalability or potential improvements.

Example Scenario:
Imagine you’re asked to explain a query fetching the total sales per region from a retail database. You’d start by describing the retail schema and sales reporting needs. Then, clarify that the query aggregates sales data grouped by region using GROUP BY. 

Next, you break down how the JOIN connects sales and region tables, and the WHERE clause filters data for the current fiscal year. Finally, you explain any indexing on the region column improving query speed and summarize how the output helps management track regional performance effectively.

Also Read: SQL Jobs for Freshers: Salary, Career Growth & Opportunities

Let’s dive into some essential tips to succeed in SQL Query Interview Questions & Answers and impress your interviewers.

Tips to Succeed in SQL Query Interviews

To excel in SQL query interview questions & answers, strong foundational knowledge and practical skills are essential. Demonstrating proficiency in SQL, HTML, CSS, and database concepts is crucial. Understanding query execution plans and indexing strategies showcases readiness for real-world data environments.

• Master Core SQL Syntax: Be fluent with SELECT, JOINs (INNER, LEFT, RIGHT), WHERE, GROUP BY, HAVING, and ORDER BY clauses, essential for building complex queries.
• Understand Data Relationships: Know how to model and query normalized relational databases; explain foreign keys and use of indexes to optimize performance.
• Write Efficient Queries: Use techniques like subqueries, CTEs, window functions, and avoid expensive operations to minimize HTTP response times when serving data to frontends.
• Explain Query Logic Clearly: When discussing queries, articulate how SQL integrates with application layers, such as RESTful APIs over HTTP or dynamic HTML tables in web apps.
• Practice Real-World Scenarios: Familiarize yourself with common business use cases like data aggregation for dashboards, filtering for report generation, and maintaining data integrity.

Example Scenario:
Suppose you’re asked to write a query to fetch the monthly sales summary for a web-based retail application. You explain how your SQL query aggregates sales data grouped by month, optimized by indexes on date columns for faster retrieval. You then link this query’s output to an HTTP API endpoint that serves JSON data consumed by a React.js frontend rendering HTML tables and charts. You also mention how minimizing joins and using window functions improves performance, ensuring quick data delivery for an interactive user experience.

Also read: PL SQL Developer Salary in India: For Freshers & Experienced

Conclusion

To confidently tackle SQL query interview questions & answers, focus on understanding the logic behind each query rather than just memorizing syntax. Interviewers value clear thinking, efficient query design, and how well you connect SQL to real-world applications, like powering APIs, React.js dashboards, or backend services in Python or Java. 

lEARNING joins, filters, window functions, and aggregations is essential for working with normalized data in scalable, containerized environments. Always explain your approach with practical relevance, showing how your SQL fits into modern software systems.

If you want to learn industry-relevant SQL skills. These are some additional courses that can help you learn SQL at its core. 

• Executive Programme in Generative AI for Leaders
• Master of Design in User Experience
• Java Object-oriented Programming

Curious which courses can help you gain expertise in SQL? Contact upGrad for personalized counseling and valuable insights. For more details, you can also visit your nearest upGrad offline center.

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