What type of JOIN combines rows from two or more tables based on a related column?

The type of JOIN that combines rows from two or more tables based on a related column is known as an inner join. This join retrieves records that have matching values in both tables involved in the join operation.

In practical terms, when you execute an inner join, the result set consists of only those rows for which there is a match between the specified columns from each table. For instance, if you have a "Customers" table and an "Orders" table, an inner join on the "CustomerID" would yield only those records where a customer has placed an order, excluding customers with no orders and orders with no corresponding customer.

Inner joins are fundamental in relational databases because they allow for streamlined data retrieval based on relationships defined through foreign keys. This enables users to analyze combined data from multiple sources effectively and is a common practice in SQL querying.

The other types of joins—such as outer join, cross join, and self join—serve different purposes. For example, outer joins include unmatched rows, cross joins produce a Cartesian product, and self joins involve a single table being joined to itself.