有没有办法在PostgreSQL函数中查询当前行值和来自同一个表的一组经过筛选的结果

-- 创建一个示例表
CREATE TABLE employees (
  id SERIAL PRIMARY KEY,
  name VARCHAR(100),
  department VARCHAR(100),
  salary NUMERIC(10, 2)
);

-- 插入一些示例数据
INSERT INTO employees (name, department, salary)
VALUES ('John Doe', 'IT', 5000),
       ('Jane Smith', 'HR', 6000),
       ('Mike Johnson', 'IT', 5500),
       ('Lisa Roberts', 'Finance', 7000),
       ('David Brown', 'IT', 5200);

-- 创建一个函数，使用窗口函数查询当前行值和来自同一个表的一组经过筛选的结果
CREATE OR REPLACE FUNCTION get_filtered_employees()
  RETURNS TABLE (id INT, name VARCHAR(100), department VARCHAR(100), salary NUMERIC(10, 2), filtered_salary NUMERIC(10, 2))
AS $$
BEGIN
  RETURN QUERY
    SELECT id, name, department, salary,
           AVG(salary) OVER (PARTITION BY department) AS filtered_salary
    FROM employees;
END;
$$ LANGUAGE plpgsql;

-- 调用函数并查询结果
SELECT * FROM get_filtered_employees();