SQL to Hired The Data Interview Guide

Breaking into the field of Data Analytics can be challenging—but with the right preparation and guidance, it’s completely achievable. Whether you’re applying for your first role or transitioning careers, this guide by ONLEI Technologies will help you confidently navigate SQL interviews and land your dream job as a Data Analyst.

🔍 Why SQL Matters in Data Analyst Interviews

SQL (Structured Query Language) is the foundation of data analytics. It allows analysts to retrieve, manipulate, and analyze data stored in relational databases. Most interviews for data analyst roles heavily test SQL knowledge.

ONLEI Technologies offers hands-on SQL training as part of its Data Analytics and Full Stack Development programs—ensuring students are job-ready from day one.

🎯 Top 10 SQL Interview Questions with Answers

1. What is SQL?

Answer:
SQL stands for Structured Query Language. It’s used to interact with databases—retrieve, update, insert, and delete data.

2. What is the difference between WHERE and HAVING clauses?

Answer:

• WHERE filters rows before grouping.
• HAVING filters groups after aggregation.
  Example: Use WHERE for filtering before GROUP BY and HAVING to filter on COUNT(), SUM(), etc.

3. Write a SQL query to find the second highest salary.

Answer:

sqlCopyEditSELECT MAX(salary) 
FROM employees 
WHERE salary < (SELECT MAX(salary) FROM employees);

4. What is a JOIN? Explain types of JOINs.

Answer:
A JOIN combines rows from two or more tables based on a related column.

• INNER JOIN: Matches in both tables
• LEFT JOIN: All from left, matches from right
• RIGHT JOIN: All from right, matches from left
• FULL OUTER JOIN: All from both, matched and unmatched

5. What does GROUP BY do in SQL?

Answer:
GROUP BY groups rows that have the same values in specified columns for aggregation like SUM, COUNT, AVG.

6. Write a query to get the total sales per region.

Answer:

sqlCopyEditSELECT region, SUM(sales) 
FROM orders 
GROUP BY region;

7. What is normalization?

Answer:
Normalization is the process of organizing data to reduce redundancy and improve integrity. It breaks large tables into smaller, related ones.

8. What is the use of LIMIT in SQL?

Answer:
LIMIT restricts the number of rows returned by a query.
Example: SELECT * FROM customers LIMIT 10;

9. What is the difference between DELETE, TRUNCATE, and DROP?

Answer:

• DELETE: Removes specific rows, can use WHERE.
• TRUNCATE: Removes all rows, faster, cannot be rolled back.
• DROP: Deletes the table structure entirely.

10. How do you find duplicate records in a table?

Answer:

sqlCopyEditSELECT column_name, COUNT(*) 
FROM table_name 
GROUP BY column_name 
HAVING COUNT(*) > 1;

🚀 How ONLEI Technologies Prepares You

At ONLEI Technologies, students receive:

• Live project experience
• One-on-one mentorship
• Mock interviews
• Job-oriented SQL and data training
• Placement assistance with real industry connections

With ONLEI’s hands-on approach, you don’t just learn theory—you solve real-world business problems.

✅ Final Tips to Ace Your SQL Interview

• Practice SQL queries daily (LeetCode, HackerRank, StrataScratch).
• Understand query optimization and read explain plans.
• Combine SQL with Excel, Python, or Tableau for bonus points.
• Be ready to explain your logic clearly during live coding rounds.

📢 Ready to Get Hired?

Start your journey with ONLEI Technologies and transform your skills into a successful data analytics career.
👉 Visit www.onleitechnologies.com to enroll or book a free career consultation today.