PostgreSQL – RIGHT JOIN
A RIGHT JOIN is used to retrieve data from two or more tables based on a specified condition, while also including all the rows from the right (or second) table, even if there is no match in the left (or first) table. This means that even if there is no matching row in the left table, the row from the right table will still be included in the result set.
The basic syntax of a RIGHT JOIN in PostgreSQL is as follows:
SELECT column_list FROM left_table RIGHT JOIN right_table ON join_condition;Here’s a breakdown of the components:
SELECT column_list: This is the list of columns you want to retrieve from the tables.left_table: The table from which you want to retrieve data and which will be on the left side of the join operation. Note that in a RIGHT JOIN, this table is often referred to as the “right” table.right_table: The table you want to join with the left table, which will be on the right side of the join operation. This is often referred to as the “left” table in a RIGHT JOIN.ON join_condition: This is the condition that specifies how the tables should be joined. It defines the relationship between the columns in the left and right tables.
Consider two tables: “orders” and “customers.” Below is the query to retrieve a list of all customers and their corresponding order information, including customers without matching orders using the Right Join.
SELECT o.order_id, o.order_date, c.customer_name FROM orders o RIGHT JOIN customers c ON o.customer_id = c.customer_id;Above query retrieves the order ID and date from the “orders” table and the customer name from the “customers” table. The RIGHT JOIN ensures that all rows from the “customers” table are included in the result, even if there is no matching order in the “orders” table.