PostgreSQL Joins and Window Function

Understanding JOINS in PostgreSQL Joins let you merge data from multiple tables (or views) by linking them through related columns. The choice of join type depends mainly on: Which rows you want to keep (including unmatched ones) How the tables relate to each other Main Join Types CROSS JOIN Creates the Cartesian product - every row from the first table pairs with every row from the second. No ON clause needed. Example result: 5 rows × 5 rows = 25 rows.SQLSELECT p.project_name, e.name, e.salary FROM sales_data.projects p CROSS JOIN sales_data.employees e; INNER JOIN Returns only matching rows from both tables. Non-matching rows are excluded SELECT emp.name, dep.department_name FROM sales_data.employees emp INNER JOIN sales_data.departments dep ON emp.department_id = dep.department_id; LEFT JOIN (LEFT OUTER JOIN) Keeps all rows from the left table, plus matching rows from the right. SELECT *FROM sales_data.projects p LEFT JOIN sales_data.employees e ON p.employee_id = e.employee_id; RIG