From http://www.w3schools.com (Copyright Refsnes Data)
With SQL, an alias name can be given to a table or to a column.
You can give a table or a column another name by using an alias. This can be a good thing to do if you have very long or complex table names or column names.
An alias name could be anything, but usually it is short.
SELECT column_name(s) FROM table_name AS alias_name |
SELECT column_name AS alias_name FROM table_name |
Assume we have a table called "Persons" and another table called "Product_Orders". We will give the table aliases of "p" an "po" respectively.
Now we want to list all the orders that "Ola Hansen" is responsible for.
We use the following SELECT statement:
SELECT po.OrderID, p.LastName, p.FirstName FROM Persons AS p, Product_Orders AS po WHERE p.LastName='Hansen' WHERE p.FirstName='Ola' |
The same SELECT statement without aliases:
SELECT Product_Orders.OrderID, Persons.LastName, Persons.FirstName FROM Persons, Product_Orders WHERE Persons.LastName='Hansen' WHERE Persons.FirstName='Ola' |
As you'll see from the two SELECT statements above; aliases can make queries easier to both write and to read.
From http://www.w3schools.com (Copyright Refsnes Data)