LEFT OUTER JOIN

The SQL LEFT JOIN, also known as LEFT OUTER JOIN, retrieves all records from the left table (table1) and the matched records from the right table (table2). If there is no match, the result set will contain NULL values for the columns from the right table.

Consider two tables, Orders and Customers, with columns as follows:

• Orders: OrderID, CustomerID, OrderDate
• Customers: CustomerID, CustomerName, City

We want to retrieve all orders along with the corresponding customer information (customer name and city), including orders without matching customers.

SELECT Orders.OrderID, Orders.OrderDate, Customers.CustomerName, Customers.City FROM Orders LEFT JOIN Customers ON Orders.CustomerID = Customers.CustomerID;

In this example, the LEFT JOIN retrieves all records from the Orders table, and only matching records from the Customers table based on the CustomerID. If there is no match for an order in the Customers table, NULL values will be returned for CustomerName and City. This ensures that all orders are included in the result set, regardless of whether they have corresponding customer information.