Day 21/30 - DEEP DIVE SOLUTIONS: SQL, PYTHON, ETL, DATA MODELING
Solutions for March 24th, 2025 Challenge – Full Breakdown + Live Runnable Code ]
Hello Data Engineers,
Today’s deep dive breaks down critical concepts in SQL Joins, Python Error Handling, ETL Retry Logic, and Data Warehouse Schema Design. Whether you're prepping for interviews or improving real-world pipelines, this breakdown will sharpen both your understanding and implementation skills.
If you haven’t upgraded yet, this is where we go beyond just knowing the answers—giving you expert breakdowns, query tuning techniques, and best practices used in production systems.
Upgrade now and stay ahead of the competition!
SQL Deep Dive: LEFT JOIN vs INNER JOIN
Challenge Recap:
❓ Which SQL join returns all records from the left table, even when there’s no match in the right table?
🔘 A) INNER JOIN
🔘 B) LEFT JOIN
🔘 C) RIGHT JOIN
🔘 D) FULL OUTER JOIN
✅ Answer: Option B - LEFT JOIN
Why This Happens:
A LEFT JOIN ensures all rows from the left table are returned, regardless of whether there's a matching row in the right table. If no match exists, NULLs are returned for columns from the right table. In contrast, INNER JOIN only returns rows with matches on both sides.
Where It’s Used in Real-World Applications:
Retrieving users with or without purchases
Auditing records where missing relationships are informative
Creating base datasets where completeness is more important than match accuracy