SQL Left Join
SQL LEFT JOIN Keyword
All records from the left table (table 1) and the matched records from the right table (table 2) are returned using the LEFT JOIN keyword. If there is no match, the outcome is 0 records from the right side.
LEFT JOIN Syntax
SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name = table2.column_name;
Note: In some databases LEFT JOIN is called LEFT OUTER JOIN.
Demo Database
We’ll be using the well-known Northwind sample database in this tutorial.
A sample from the “Customers” table is shown below:
| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 1 |
Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
And a selection from the “Orders” table:
| OrderID | CustomerID | EmployeeID | OrderDate | ShipperID |
|---|---|---|---|---|
| 10308 | 2 | 7 | 1996-09-18 | 3 |
| 10309 | 37 | 3 | 1996-09-19 | 1 |
| 10310 | 77 | 8 | 1996-09-20 | 2 |
SQL LEFT JOIN Example
The SQL query that follows will choose every customer and any orders that they may have:
Example
SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;
Note: Even in cases where there are no matches in the right table (Orders), the LEFT JOIN keyword retrieves all records from the left table (Customers).
