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Top 30 SQL Interview Questions (2025)

The most commonly asked SQL interview questions — from basic SELECT queries to advanced window functions, subqueries and optimization tips.

2025-01-15·12 min read
SQL BasicsJOINs

SQL JOINs Explained with Real Examples

INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN — explained clearly with diagrams and runnable examples on real data.

2025-01-10·8 min read

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GROUP BY vs HAVING: What's the Difference?

Most beginners confuse GROUP BY and HAVING. This guide explains the difference clearly, with examples you can run right here.

5 min read

SQL Window Functions: A Complete Guide

ROW_NUMBER, RANK, DENSE_RANK, LAG, LEAD, PARTITION BY — everything you need to know about window functions with practical examples.

10 min read

Learn SQL for Free in 2025 — Complete Roadmap

A step-by-step guide to learning SQL from scratch. Free resources, practice platforms, and a curriculum to go from beginner to job-ready.

7 min read

SQL Subqueries: Correlated, Scalar, and Inline Views

Master subqueries with clear explanations of correlated vs non-correlated subqueries, scalar subqueries, and inline views.

9 min read

CTEs (Common Table Expressions) — A Practical Guide

The WITH clause makes complex SQL readable. Learn how to use CTEs for recursive queries, running totals, and multi-step logic.

7 min read

10 SQL Performance Tips Every Developer Should Know

Write faster SQL queries with these proven optimization techniques — covering indexes, EXPLAIN plans, N+1 problems and more.

11 min read

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