JOINs

SQL JOINs let you combine data from two or more tables based on a related column between them. Think of it as linking information together to get a more complete view. The four most commonly used are: INNER JOIN, which returns rows only when there is a match in both tables; LEFT JOIN, which returns all rows from the left table and the matched rows from the right table (or NULL if there's no match); RIGHT JOIN, which returns all rows from the right table and the matched rows from the left table (or NULL if there's no match); and FULL OUTER JOIN, which returns all rows when there is a match in one of the tables.