1. sql
  2. /joins
  3. /right-join

SQL RIGHT JOIN Keyword

Definition

In SQL, a RIGHT JOIN returns all records from the right table (table2), and any matching records from the left table (table1). If there is no match in the left table, the result will contain NULL values. The syntax for a RIGHT JOIN is as follows:

SELECT column1, column2
FROM table1 
RIGHT JOIN table2 
ON table1.column_name = table2.column_name;

It is important to note that in a right join only the table which comes after the right join will return the non-matching rows. It is also an equivalent of using a LEFT JOIN and swapping the order of the tables, for example:

SELECT column1, column2 
FROM table2 
LEFT JOIN table1
ON table1.column_name = table2.column_name;

It is also possible to use the NATURAL JOIN keyword in place of ON keyword and the join condition is automatically added for columns with the same name.

Examples

Here is an example of a SQL query that uses a RIGHT JOIN to retrieve data from two tables:

SELECT * 
FROM orders 
RIGHT JOIN customers 
ON orders.customer_id = customers.id;

In this example, the query retrieves all rows from the customers table and any matching rows from the orders table. The ON clause specifies the join condition, which is that the customer_id column in the orders table must match the id column in the customers table. If an id in the customers table does not match any row in the orders table, the result will show NULL in the columns of the orders table.

Best Practices

Some best practices for using RIGHT JOIN in SQL include:

  • Use the RIGHT JOIN sparingly, as it can make your query harder to read and understand. If possible, use a LEFT JOIN and reverse the order of the tables in the query.

  • When using a RIGHT JOIN, make sure to qualify all column references with the appropriate table name or alias to avoid confusion and ensure that the query returns the correct results.

  • When joining multiple tables together, start with the smallest table on the right side of the join to optimize query performance.

  • Avoid using subqueries or derived tables on the right side of a RIGHT JOIN, as this can make the query slower and harder to maintain.

  • If possible, use the WHERE clause to filter the data after the join instead of the ON clause, to improve the performance.

  • Try to keep the join condition as simple as possible and avoid using complex expressions in the ON clause to maintain readability and performance.