Recursive Common Table Expressions (CTEs) | Employee and Manager Hierarchy example

A Recursive Common Table Expression (CTE) is a type of CTE that references itself to retrieve hierarchical or sequential data. Recursive CTEs are useful when dealing with data structures like organizational charts, file systems, or any situation involving parent-child relationships. A recursive CTE consists of two main parts: the Anchor Member, which is the starting point of the recursion, and the Recursive Member, which refers back to the CTE itself. The syntax of a recursive CTE includes the WITH RECURSIVE clause, followed by the CTE name, and the SELECT statements for the Anchor Member and Recursive Member. The example provided demonstrates how to use a recursive CTE to find all employees who report to a particular manager in an organizational hierarchy. The Anchor Member selects the top-level manager, and the Recursive Member finds employees who report to the current manager. The recursion continues until no more employees are found who report to the managers in the previous level. The final output shows the hierarchy of employees, with each level indicating the depth in the hierarchy. Recursive CTEs are extremely useful for querying hierarchical data and can be adapted to various scenarios, such as processing directory structures, product categories, or any parent-child relationships. The approach can be used to answer questions like "Who is reporting to whom?" and to explore hierarchical data. The use of recursive CTEs simplifies the process of querying complex hierarchical data structures.