Expanding the Dataset: A Comprehensive Guide to SQL Joins and Window Functions

Joins and Window Functions in SQL Joins and Window Functions in SQL are two concepts that significantly elevate querying skills. These tools allow you to combine datasets and perform advanced calculations without collapsing your data. PART 1: JOINS A Join combines rows from two or more tables based on a related column between them (usually a primary key and a foreign key). Common Types of Joins 1. INNER JOIN Returns only matching records from both tables. Customers customer_id | name 1 | Alice 2 | Bob Orders order_id | customer_id | amount 101 | 1 | 500 102 | 3 | 300 Query SELECT c.name, o.amount FROM Customers c INNER JOIN Orders o ON c.customer_id = o.customer_id; Result Alice | 500 Bob is excluded because he has no matching order. 2. LEFT JOIN (LEFT OUTER JOIN) Returns all records from the left table, and matching records from the right table. SELECT c.name, o.amount FROM Customers c LEFT JOIN Orders o ON c.customer_id = o.customer_id; Result Alice | 500 Bob | NULL Bob appears with