What does the ON keyword specify in an INNER JOIN?

In an INNER JOIN, the ON keyword specifies the condition that defines how the two tables are related. It is used to indicate which columns from each table should be compared to find matching rows.

Purpose of the ON Keyword:

1. Join Condition: The ON clause contains the criteria that determine which rows from the first table match with rows from the second table. This is typically based on a foreign key relationship.

2. Column Specification: You specify the columns from each table that should be compared. The condition usually involves equality (e.g., table1.column = table2.column).

Example:

Here’s a simple example of an INNER JOIN using the ON keyword:

SELECT orders.order_id, customers.first_name
FROM orders
INNER JOIN customers ON orders.customer_id = customers.customer_id;

In this example:

• orders is the first table, and customers is the second table.
• The ON clause specifies that the customer_id column in the orders table should match the customer_id column in the customers table.
• Only rows where this condition is true will be included in the result set.

Overall, the ON keyword is essential for defining the relationship between the tables being joined.