SQL Aliases

SQL aliases provide temporary, alternative names for tables or columns within a single query. They make your SQL more readable and easier to understand, particularly in complex queries.

Creating Aliases

Using the AS Keyword

Aliases are created using the AS keyword. While the AS keyword is often used, it's actually optional in many database systems.

Syntax (with AS)


SELECT column_name AS alias_name
FROM table_name;

Example: Simple Column Alias

Syntax


SELECT CustomerID AS ID FROM Customers;

Output


ID
--
(CustomerID values from the Customers table)

Optional AS Keyword

The AS keyword is optional in many database systems. This shorter syntax achieves the same result:

Syntax


SELECT CustomerID ID FROM Customers;

Output


ID
--
(CustomerID values from the Customers table)

Aliases with Spaces

If your alias needs spaces, enclose it in square brackets [] or double quotes "".

Syntax


SELECT ProductName AS "My Great Product" FROM Products; --Using double quotes
SELECT ProductName AS [My Great Product] FROM Products; --Using square brackets

Output


My Great Product
-----------------
(ProductName values from the Products table)

Creating Aliases for Tables

The same AS keyword is used to create aliases for tables. This is particularly useful when joining multiple tables.

Syntax


SELECT column_name(s) FROM table_name AS alias_name;

Example: Table Alias

Syntax


SELECT * FROM Customers AS Persons;

Output


(All columns and rows from the Customers table will be displayed.)

Combining Columns into a Single Alias

This creates an alias 'Address' by combining several columns. (Assumes a 'Customers' table with 'Address', 'PostalCode', 'City', and 'Country' columns).

Syntax (SQL Server)


SELECT CustomerName, Address + ', ' + PostalCode + ' ' + City + ', ' + Country AS Address
FROM Customers;

Syntax (MySQL)


SELECT CustomerName, CONCAT(Address,', ',PostalCode,', ',City,', ',Country) AS Address
FROM Customers;

Syntax (Oracle)


SELECT CustomerName, (Address || ', ' || PostalCode || ' ' || City || ', ' || Country) AS Address
FROM Customers;

Output


CustomerName | Address
-------------------------------------------------
(Customer names and their combined address information)

Table Aliases in a JOIN

Using aliases to shorten a query involving two tables ('Customers' and 'Orders'). (Assumes 'Customers' and 'Orders' tables exist with linking columns).

Syntax


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;

Output


OrderID | OrderDate | CustomerName
-----------------------------------
(Orders for 'Around the Horn' will be displayed here.)