Recursive CTE Employee Hierarchy Query – Employeeid Sql

Task: Write a complete, production‑ready solution for retrieving an employee hierarchy using a recursive Common Table Expression (CTE) in SQL Server (or PostgreSQL compatible syntax). The solution must include the SQL query, a brief explanation of how it works, sample data insertion statements, an example of the expected result set, and performance considerations (including index recommendations and cycle detection).

Requirements:

1. Schema Definition

   • Table name: Employees
   • Columns:
     • EmployeeID (INT, primary key)
     • EmployeeName (NVARCHAR(100), NOT NULL)
     • ManagerID (INT, NULL, foreign key referencing Employees.EmployeeID)
     • Title (NVARCHAR(100), NOT NULL)
     • HireDate (DATE, NOT NULL)
   • Provide a CREATE TABLE statement that includes primary key and foreign‑key constraints.

2. Sample Data

   • Insert at least 10 rows that form a multi‑level hierarchy (e.g., CEO → VP → Director → Manager → Staff).
   • Include at least one case where ManagerID is NULL (top‑level) and one case that would create a cycle if not handled (e.g., Employee 9 reports to Employee 5, and Employee 5 reports to Employee 9). Show how the cycle is prevented.

3. Recursive CTE Query

   • The query must accept a parameter @RootEmployeeID (or $root_id for PostgreSQL) to start the hierarchy at any employee.
   • Output columns:
     1. EmployeeID
     2. EmployeeName
     3. Title
     4. HireDate
     5. ManagerID
     6. HierarchyLevel (1 for the root, 2 for direct reports, etc.)
     7. Path – a string showing the chain of EmployeeIDs from the root to the current row, separated by > (e.g., 1>4>7).
   • Include a safeguard against infinite recursion (e.g., OPTION (MAXRECURSION 1000) for SQL Server or MAXRECURSION equivalent).
   • Order the final result set by Path.

4. Explanation

   • Provide a concise (≤150 words) description of how the recursive CTE builds the hierarchy, how HierarchyLevel and Path are calculated, and how the cycle‑prevention logic works.

5. Performance & Indexing

   • Recommend at least one index (or index combination) that optimizes the recursive query.
   • Explain why the index helps and any trade‑offs.
   • Mention any additional settings (e.g., SET ANSI_NULLS ON) that are advisable for production.

6. Output Format

   • All SQL code must be enclosed in triple backticks with the appropriate language tag (sql).
   • The explanation and performance notes should be plain text sections with clear headings.
   • Example result set should be presented as a markdown table.

Expected Output Example:

-- 1. Table creation
CREATE TABLE Employees ( ... );

-- 2. Sample data
INSERT INTO Employees ...;

-- 3. Recursive CTE query
DECLARE @RootEmployeeID INT = 1;
WITH EmployeeHierarchy AS ( ... )
SELECT ...;
OPTION (MAXRECURSION 1000);

Explanation: Your brief description here.

Performance & Indexing: Your recommendations here.

Sample Result Set

EmployeeID	EmployeeName	Title	HireDate	ManagerID	HierarchyLevel	Path
1	Alice Smith	CEO	2005-03-01	NULL	1	1
2	Bob Jones	VP Marketing	2008-07-15	1	2	1>2
…	…	…	…	…	…	…

Deliver the entire response exactly as described, with no additional commentary.