PostgreSQL - Window Functions

Create table 'employees'

CREATE TABLE employees (emp_id integer primary key, fname varchar(50), lname varchar(50), email varchar(100), dept varchar(50), salary numeric(10,2), hire_date date);


INSERT INTO employees (emp_id, fname, lname, email, dept, salary, hire_date) 
  VALUES
(1, 'Raj', 'Sharma', 'raj.sharma@example.com', 'IT', 50000.00, '2020-01-15'),
(2, 'Priya', 'Singh', 'priya.singh@example.com', 'HR', 45000.00, '2019-03-22'),
(3, 'Arjun', 'Verma', 'arjun.verma@example.com', 'IT', 55000.00, '2021-06-01'),
(4, 'Suman', 'Patel', 'suman.patel@example.com', 'Finance', 60000.00, '2018-07-30'),
(5, 'Kavita', 'Rao', 'kavita.rao@example.com', 'HR', 47000.00, '2020-11-10'),
(6, 'Amit', 'Gupta', 'amit.gupta@example.com', 'Marketing', 52000.00, '2020-09-25'),
(7, 'Neha', 'Desai', 'neha.desai@example.com', 'IT', 48000.00, '2019-05-18'),
(8, 'Rahul', 'Kumar', 'rahul.kumar@example.com', 'IT', 53000.00, '2021-02-14'),
(9, 'Anjali', 'Mehta', 'anjali.mehta@example.com', 'Finance', 61000.00, '2018-12-03'),
(10, 'Vijay', 'Nair', 'vijay.nair@example.com', 'Marketing', 50000.00, '2020-04-19')
 [Ref](https://www.youtube.com/watch?v=cnzka7kF5Zk)