Extended Intermediate PostgreSQL Exercises with 10 Advanced Scenarios

[LetitiaGilbert]

📝 Description

This pull request extends the existing intermediate-exercises.md file with 10 new advanced-level exercises.
Each exercise follows the same format — Scenario → Context → Question → Answer → Explanation — to maintain consistency with the current repository style.

The new additions focus on practical, real-world PostgreSQL use cases that build on the intermediate concepts, helping learners explore more advanced query techniques and database features.

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🧩 Topics Covered

• Recursive Common Table Expressions (CTEs)
• Lateral joins for correlated subqueries
• Advanced JSONB filtering and nested key extraction
• Window functions with ranking and partitioning
• Materialized views and refresh strategies
• Table partitioning concepts
• Transaction isolation and concurrency control
• Array aggregation
• Full-text search with ranking (ts_rank_cd)
• Combined multi-feature query scenarios

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✅ Purpose

These exercises:

• Expand the learning depth of the intermediate level
• Provide practical SQL challenges relevant to real-world PostgreSQL applications
• Serve as a natural bridge between intermediate and advanced topics

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🧠 Notes

All exercises have been written to match the tone, formatting, and structure of the existing materials.
Each query has been tested for syntax accuracy and clarity.

[fahimahammed]

thank you