SQL Aliases

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SQL Aliases
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SQL Aliases
SQL aliases are used to give a table, or a column in a table, a temporary name.

Aliases are often used to make column names more readable.

An alias only exists for the duration of the query.

Alias Column Syntax
SELECT column_name AS alias_name
FROM table_name;
Alias Table Syntax
SELECT column_name(s)
FROM table_name AS alias_name;
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
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
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
And a selection from the "Orders" table:

OrderID CustomerID EmployeeID OrderDate ShipperID
10354 58 8 1996-11-14 3
10355 4 6 1996-11-15 1
10356 86 6 1996-11-18 2
Alias for Columns Examples
The following SQL statement creates two aliases, one for the CustomerID column and one for the CustomerName column:

Example
SELECT CustomerID as ID, CustomerName AS Customer
FROM Customers;
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The following SQL statement creates two aliases, one for the CustomerName column and one for the ContactName column. Note: It requires double quotation marks or square brackets if the alias name contains spaces:

Example
SELECT CustomerName AS Customer, ContactName AS [Contact Person]
FROM Customers;
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The following SQL statement creates an alias named "Address" that combine four columns (Address, PostalCode, City and Country):

Example
SELECT CustomerName, Address + ', ' + PostalCode + ' ' + City + ', ' + Country AS Address
FROM Customers;
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Note: To get the SQL statement above to work in MySQL use the following:

SELECT CustomerName, CONCAT(Address,', ',PostalCode,', ',City,', ',Country) AS Address
FROM Customers;
Alias for Tables Example
The following SQL statement selects all the orders from the customer with CustomerID=4 (Around the Horn). We use the "Customers" and "Orders" tables, and give them the table aliases of "c" and "o" respectively (Here we use aliases to make the SQL shorter):

Example
SELECT o.OrderID, o.OrderDate, c.CustomerName
FROM Customers AS c, Orders AS o
WHERE c.CustomerName="Around the Horn" AND c.CustomerID=o.CustomerID;
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The following SQL statement is the same as above, but without aliases:

Example
SELECT Orders.OrderID, Orders.OrderDate, Customers.CustomerName
FROM Customers, Orders
WHERE Customers.CustomerName="Around the Horn" AND Customers.CustomerID=Orders.CustomerID;
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Aliases can be useful when:

There are more than one table involved in a query
Functions are used in the query
Column names are big or not very readable
Two or more columns are combined together

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