To perform a SQL join, you can use the JOIN keyword in your SQL query to combine rows from two or more tables based on a related column between them. There are four types of SQL joins: inner join, left join, right join, and full join.

Here's an example of how to perform an inner join in SQL:

SELECT * FROM table1
INNER JOIN table2 ON table1.column = table2.column;

LEFT JOIN returns all rows from the left table, and the matched rows from the right table. If there is no match, the result is NULL on the right side.

In this example, the INNER JOIN clause is used to combine rows from the table1 table and the table2 table where the columns matches. The SELECT statement specifies the columns that should be included in the result set.

Here's an example of how to perform a left join in SQL:

SELECT orders.order_id, customers.customer_name
FROM orders
LEFT JOIN customers ON orders.customer_id = customers.customer_id;

In this example, the LEFT JOIN clause is used to return all rows from the orders table and the matching rows from the customers table. If there are no matching rows in the customers table, NULL values will be displayed.

You can also perform a right join or a full join using the RIGHT JOIN or FULL JOIN clause respectively. The syntax for these joins is similar to the left join.

Here's an example of how to perform a full join in SQL:

SELECT orders.order_id, customers.customer_name
FROM orders
FULL JOIN customers ON orders.customer_id = customers.customer_id;

In this example, the FULL JOIN clause is used to return all rows from both the orders table and the customers table, with NULL values displayed where there are no matching rows.