Day 23/30 - DEEP DIVE SOLUTIONS: SQL, PYTHON, ETL, DATA MODELING
Solutions for March 26th, 2025 Challenge – Full Breakdown + Live Runnable Code
Hello Data Engineers,
You’ve crossed into the final stretch. Today’s challenges dive into recursive SQL CTEs, functional programming in Python, incremental load efficiency, and denormalization trade-offs in modeling. These are essential tools in both system design and interviews. Let’s break them down.
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SQL Deep Dive: Recursive CTEs for Hierarchies
Challenge Recap:
❓ What will this recursive SQL CTE most likely be used for?
🔘 A) Generating running totals
🔘 B) Flattening nested JSON
🔘 C) Traversing hierarchical parent-child relationships
🔘 D) Optimizing join performance
✅ Answer: Option C - Traversing hierarchical parent-child relationships
Why This Happens:
Recursive CTEs repeatedly reference themselves to navigate hierarchical structures like org charts, category trees, and directory paths. They continue looping until a base condition fails.
Where It’s Used in Real-World Applications:
Org chart traversal
Folder and file system modeling
Multi-level product categories
Hierarchical menu rendering