Recursive CTE
A Recursive Common Table Expression (CTE) is a SQL feature that allows a query to reference itself, enabling iterative or hierarchical data processing within a single SQL statement. It is commonly used to traverse tree-like structures, such as organizational charts, file systems, or bill-of-materials, by repeatedly applying a union of base and recursive parts until a termination condition is met. This provides a declarative way to handle recursive data without procedural loops or multiple queries.
Developers should learn Recursive CTEs when working with hierarchical or graph-based data in SQL databases, such as querying parent-child relationships, calculating cumulative sums, or generating sequences. It is particularly useful in scenarios like organizational reporting, product assembly trees, or social network analysis, as it simplifies complex recursive logic into a single, readable query, improving performance and maintainability compared to iterative approaches in application code.