SQL Subqueries & CTEs Explained | Data Engineering Live Session 4

🚀 Session 4 of the Data Engineering Roadmap is LIVE! Today we go deep on two SQL concepts that separate beginners from professionals — Subqueries and CTEs (Common Table Expressions). Master these and your SQL will never be the same. 📌 What We Cover: 🔷 SUBQUERIES — Queries inside queries: ✅ Scalar Subqueries (return single value) ✅ Correlated Subqueries (row-by-row execution) ✅ Subqueries in WHERE, FROM & SELECT ✅ EXISTS vs IN — when to use which ✅ Performance implications & gotchas 🔷 CTEs (Common Table Expressions): ✅ WITH clause — syntax & structure ✅ Chaining multiple CTEs together ✅ Recursive CTEs for hierarchical data ✅ CTE vs Subquery — when to use which ✅ Real-world interview patterns 💡 Hands-on live coding with real datasets throughout.