Find the second highest salary from the Employee table. Find duplicate records in a table. Retrieve employees who earn more than their manager. Count employees in each department having more than 5 employees. Find employees who joined in the last 6 months. Get departments with no employees. Write a query to find the median salary. … Read more
Introduction If you are starting a career in technology—especially in Data Engineering—there is one skill you will repeatedly hear about: SQL. Some beginners ignore it because they think modern tools like Python, AI, or cloud platforms are more important. Others underestimate it because it looks “too simple.” But here is the truth: SQL is the … Read more
Introduction As your database grows, you may start to notice that your SQL queries become slower. Simple queries that once took milliseconds may begin to take seconds—or even longer. This can impact application performance, user experience, and overall system efficiency. One of the most effective ways to solve this problem is SQL indexing. Indexing is … Read more
Introduction In real-world databases, data is rarely stored in a single table. Instead, it is distributed across multiple related tables to improve organization, reduce duplication, and maintain consistency. While this structure is efficient, it also creates a challenge: how do you combine data from different tables to get meaningful results? This is where SQL JOINs … Read more
What is Data? Data is nothing but raw and unprocessed facts and statistics stored or free flowing over a network. Data becomes information when it is processed, turning it into something meaningful. Collecting and storing data for analysis is a human activity and we have been doing it for thousands of years. In order to … Read more
Introduction When starting a career in data analysis, one of the most common questions is: Should I learn Excel or SQL first? Both tools are widely used in the industry, but they serve different purposes. Excel is popular for quick analysis and visualization, while SQL is used for handling large datasets stored in databases. In this … Read more