Hierarchy Operator

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Purpose: Used to query hierarchical data using a parent-child relationship.Syntax:

SELECT column1, column2, LEVEL FROM table_name START WITH condition CONNECT BY PRIOR parent_column = child_column;

Example:

SELECT employee_id, first_name, manager_id, LEVEL
FROM employees
START WITH manager_id IS NULL
CONNECT BY PRIOR employee_id = manager_id;

Explanation: This retrieves a hierarchy of employees starting from those without a manager (top level).

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