Advanced Scenarios with Common Table Expressions (CTE) in SQL Server

Create a Recursive CTE for Category Hierarchy

Write a recursive CTE to retrieve all subcategories for a given category in a product catalog.

Expected output: A list of categories with their hierarchy levels starting from the specified root.

Hint: Start with the root category as the anchor member and recursively join on parent category ID.

Chain Multiple CTEs for Sales Analysis

Use multiple CTEs to filter sales data by date, calculate monthly totals, and then find the top-selling products.

Expected output: A result set showing top products with monthly sales totals.

Hint: Define one CTE for filtering, one for aggregation, and a final SELECT to filter top products.

A recursive CTE is a Common Table Expression that references itself to perform iterative operations, commonly used to query hierarchical data such as organizational charts or folder structures.

Multiple CTEs allow breaking down complex queries into smaller, manageable parts that can be referenced sequentially, improving readability and maintainability.

CTEs are inlined during query optimization, so they do not inherently improve performance. Recursive CTEs can be costly, and indexing key columns and filtering data are important to maintain efficiency.