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The INNER JOIN command returns rows that have matching values in both tables
The INNER JOIN
command returns rows that have matching values in both tables.
The following SQL selects all orders with customer information:
SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN
Customers ON Orders.CustomerID = Customers.CustomerID;
The following SQL statement selects all orders with customer and shipper information:
SELECT Orders.OrderID, Customers.CustomerName, Shippers.ShipperName
FROM
((Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID)
INNER JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID);
The LEFT JOIN
command returns all rows from
the left table, and the matching rows from the right table. The result is NULL
from the right side, if there is no match.
The following SQL will select all customers, and any orders they might have:
SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders
ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;
LEFT JOIN
keyword returns all records from the
left table (Customers), even if there are no matches in the right table
(Orders).
The RIGHT JOIN
command returns all rows from
the right table, and the matching records from the left table. The result is
NULL from the left side, when there is no match.
The following SQL will return all employees, and any orders they might have placed:
SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
FROM Orders
RIGHT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
ORDER BY Orders.OrderID;
RIGHT JOIN
keyword returns all records from the
right table (Employees), even if there are no matches in the left table
(Orders).
The FULL OUTER JOIN
command returns all rows
when there is a match in either left table or right table.
The following SQL statement selects all customers, and all orders:
SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
FULL OUTER JOIN Orders
ON Customers.CustomerID=Orders.CustomerID
ORDER BY Customers.CustomerName;
FULL OUTER JOIN
keyword returns all the rows from
the left table (Customers), and all the rows from the right table (Orders). If
there are rows in "Customers" that do not have matches in "Orders", or if there
are rows in "Orders" that do not have matches in "Customers", those rows will be
listed as well.