Mastering SQL: Top 50 Technical Questions to Ace Your Next Data Interview

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Introduction

SQL is the cornerstone of data manipulation and analysis in the tech industry. Whether you’re aiming for a role as a Data Analyst, Data Engineer, or Data Scientist, SQL proficiency is essential. This article covers the top 50 SQL questions you might encounter in interviews, complete with solutions and business contexts to help you understand their real-world applications.

Table of Contents

1. Basic SQL Queries
2. Data Transformation and Cleaning
3. Aggregations and Grouping
4. Joins and Subqueries
5. Advanced SQL Techniques
6. Performance Optimization
7. Real-world Business Applications

Basic SQL Queries

1. Retrieve All Employees

Question: How do you select all columns from the employee table?

SELECT * FROM employee;

Business Context: This query is fundamental for retrieving complete datasets for initial analysis or reporting.

2. Select Specific Columns