Tóm Tắt
SQL
FULL OUTER JOIN
Keyword
SQL FULL OUTER JOIN Keyword
The FULL OUTER JOIN
keyword returns all records when there is a match in
left (table1) or right (table2) table records.
Tip: FULL OUTER JOIN
and
FULL JOIN
are the same.
FULL OUTER JOIN Syntax
SELECT column_name(s)
FROM table1
FULL OUTER JOIN table2
ON table1.column_name = table2.column_name
WHERE condition;
Note: FULL OUTER JOIN
can potentially return very large
result-sets!
Demo Database
In this tutorial we will use the well-known Northwind sample database.
Below is a selection from the “Customers” table:
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 FULL OUTER JOIN Example
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;
A selection from the result set may look like this:
CustomerName
OrderID
Null
10309
Null
10310
Alfreds Futterkiste
Null
Ana Trujillo Emparedados y helados
10308
Antonio Moreno Taquería
Null
Note: The FULL OUTER JOIN
keyword returns all matching
records from both tables whether the other table matches or not. So, 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.