SQL Interview Questions Part 2 | Advanced Level | Data Engineering Live Session #6

🔥 We're BACK with Part 2 of SQL Interview Questions! Session 6 is the direct continuation of Session 5 — if you haven't watched that yet, go watch it first. Today we go even DEEPER with harder, more complex questions that are actually asked at top companies. ───────────────────────────────────────── 📌 WHAT WE SOLVE IN THIS SESSION: ───────────────────────────────────────── 🔥 ADVANCED Window Function Questions: ✅ Find customers with purchases on 3 consecutive days ✅ Calculate session gaps between user events ✅ LAG/LEAD for month-over-month growth comparisons 🔁 Recursive CTE Questions: ✅ Build an org chart — find all reports under a manager ✅ Traverse hierarchical data (Bill of Materials) ✅ Recursive date series generation 🔗 Advanced JOIN Questions: ✅ Detect duplicate transactions using SELF JOIN ✅ Many-to-many relationships with bridge tables ✅ Anti-joins for gap analysis 📊 Complex GROUP BY Questions: ✅ Monthly user retention rate calculation ✅ Day-over-day & week-over-week active users ✅ Cohort analysis using GROUP BY + CASE 🔀 Advanced SQL Patterns: ✅ PIVOT rows to columns — dynamic monthly sales ✅ UNPIVOT for normalizing wide tables ✅ CASE WHEN for conditional aggregation tricks