How do Common Table Expressions (CTEs) help in writing recursive queries in SQL Server?

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Khushi Singh · Answer

Common Table Expressions (CTEs) are handy when writing recursive queries in
SQL Server. They let you create a temporary result set that can reference itself, which helps in working with hierarchical data like employee-manager relationships or folder structures. A recursive CTE has two main parts: 1. **Anchor member** – this part gets the initial set of rows. 2. **Recursive member** – this part references the CTE itself to get the next level of data. You put these parts together with a UNION ALL, and SQL Server will keep running the recursive member until it can’t find any new rows. This builds up the full result set step by step. Using a CTE, you can easily pull the entire employee hierarchy, starting from the top manager all the way down. CTEs make things simpler than trying to write complicated code or using several joins, making recursive queries more straightforward and easier to work with.
WITH EmployeeHierarchy AS (
   SELECT EmployeeID, ManagerID, Name
   FROM Employees
   WHERE ManagerID IS NULL  -- Anchor member (top-level manager)
   UNION ALL
   SELECT e.EmployeeID, e.ManagerID, e.Name
   FROM Employees e
   INNER JOIN EmployeeHierarchy eh ON e.ManagerID = eh.EmployeeID  -- Recursive member
)
SELECT * FROM EmployeeHierarchy;

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How do Common Table Expressions (CTEs) help in writing recursive queries in SQL Server?

Ashutosh Kumar Verma

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