Find Employees with the Highest Performance Rating in Each Department Query Using MS SQL Server?

To find the employees with the highest performance rating in each department using Microsoft SQL Server, you typically need a table structure that includes:

• An Employees table with columns for EmployeeID, DepartmentID, PerformanceRating, and possibly other employee details.
• A Departments table with columns for DepartmentID and DepartmentName (if you want to include department names).

Here’s how you can write a SQL query to achieve this:

SQL Query

-- Find employees with the highest performance rating in each department

WITH MaxRatings AS (

    SELECT

        DepartmentID,

        MAX(PerformanceRating) AS MaxRating

    FROM

        Employees

    GROUP BY

        DepartmentID

)

SELECT

    e.EmployeeID,

    e.DepartmentID,

    e.PerformanceRating,

    d.DepartmentName -- Optional: Include department name if you have a Departments table

FROM

    Employees e

    JOIN MaxRatings mr ON e.DepartmentID = mr.DepartmentID AND e.PerformanceRating = mr.MaxRating

    LEFT JOIN Departments d ON e.DepartmentID = d.DepartmentID -- Optional: Join with Departments table

ORDER BY

    e.DepartmentID, e.PerformanceRating DESC;

Explanation

1. MaxRatings CTE:

   • This Common Table Expression calculates the highest performance rating for each department.
   • MAX(PerformanceRating) AS MaxRating: Finds the maximum rating for each department.
   • GROUP BY DepartmentID: Groups the results by department.

2. Main Query:

   • Joins the Employees table with the MaxRatings CTE to filter out employees who have the highest rating within their department.
   • LEFT JOIN Departments d ON e.DepartmentID = d.DepartmentID: Optionally join with the Departments table to get department names if needed.
   • ORDER BY e.DepartmentID, e.PerformanceRating DESC: Orders the results by department and performance rating.

Additional Considerations

• Handling Ties: If multiple employees have the highest performance rating within the same department, this query will include all such employees.

• Including Department Information: If you want to include the department name, ensure you have a Departments table and join it as shown.

• Performance: For large datasets, ensure that the PerformanceRating and DepartmentID columns are indexed to improve query performance.

Adjust the column names and table structures according to your actual database schema. This query provides a clear method to identify the top-performing employees by department.