SQL JOIN combines rows from two or more tables based on related columns. Understanding JOINs is essential for working with relational databases.

Types of SQL JOINs

INNER JOIN: Returns matching rows from both tables

LEFT JOIN: Returns all rows from left table + matches from right

RIGHT JOIN: Returns all rows from right table + matches from left

FULL JOIN: Returns all rows when there's a match in either table

INNER JOIN Example

SELECT orders.id, customers.name, orders.total

FROM orders

INNER JOIN customers ON orders.customer_id = customers.id;

LEFT JOIN Example

SELECT customers.name, orders.id

FROM customers

LEFT JOIN orders ON customers.id = orders.customer_id;

Multiple JOINs

SELECT o.id, c.name, p.product_name

FROM orders o

JOIN customers c ON o.customer_id = c.id

JOIN products p ON o.product_id = p.id;

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