Day 24/30 - DEEP DIVE SOLUTIONS: SQL, PYTHON, ETL, DATA MODELING
Solutions for March 27th, 2025 Challenge – Full Breakdown + Live Runnable Code
Hello Data Engineers,
Today we’re diving into index optimization, list comprehensions with filters, ETL orchestration tools, and Slowly Changing Dimensions (SCDs). Whether you’re building scalable data platforms or preparing for a technical interview, this breakdown is a must-study.
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: Indexes and Query Optimization
Challenge Recap:
❓ Which query would benefit MOST from adding an index on the email column?
🔘 A) SELECT * FROM users WHERE email = 'x@example.com'
🔘 B) SELECT COUNT(*) FROM users
🔘 C) SELECT * FROM users ORDER BY id DESC
🔘 D) SELECT DISTINCT department FROM users
✅ Answer: Option A - SELECT * FROM users WHERE email = 'x@example.com'
Why This Happens:
Indexes improve performance only when a query filters rows using a specific column. Filtering by email is a perfect candidate for an index. The other options either scan the entire table or don’t benefit from an index on email.
Where It’s Used in Real-World Applications:
User lookup by email or username
Customer support systems querying accounts by email
Authentication systems