What is the SQL AS keyword used for?

AS is used to assign an alias — a temporary, alternative name — to a column or table within a SQL query. The alias exists only for the duration of that query.

Is there a functional difference between using AS and omitting it?

No. Writing column_name alias and column_name AS alias produce identical results. AS is simply the explicit, more readable form.

Can I use a column alias in a WHERE clause?

In most databases, column aliases defined in SELECT cannot be referenced in the WHERE clause of the same query. You would need to use a subquery or repeat the expression instead.

When should I use a table alias with AS?

Table aliases are useful when joining multiple tables, when referencing the same table more than once (self-join), or simply to shorten long table names in complex queries.

SQL AS

SQL > SQL Commands > AS

The keyword AS is used to assign an alias to the column or a table. It is inserted between the column name and the column alias or between the table name and the table alias.

SQL AS explicitly labels a column or table with a temporary alias, making query results and complex expressions easier to read — there is no functional difference between using AS and omitting it.

Syntax

The syntax for using AS is as follows:

SELECT "table_alias"."column_name1" AS "column_alias"
FROM "table_name" AS "table_alias";

Example

Let's take a look at the same example as we used in the SQL Alias section. Assume we have the following table, Store_Information,

Table Store_Information

Store_Name	Sales	Txn_Date
Los Angeles	1500	Jan-05-1999
San Diego	250	Jan-07-1999
Los Angeles	300	Jan-08-1999
Boston	700	Jan-08-1999

To find total sales by store using AS as part of the table and column alias, we type in:

SELECT A1.Store_Name Store, SUM(A1.Sales) AS "Total Sales"
FROM Store_Information AS A1
GROUP BY A1.Store_Name;

Result:

Store		Total Sales
Los Angeles		1800
San Diego		250
Boston		700

Is there a difference between using an alias without AS and with AS in SQL? The answer is no, there is no functional difference, as both versions will accomplish exactly the same thing. The use of AS is simply a more explicit way of mentioning the alias.

Frequently Asked Questions

What does SQL AS do?: AS assigns a temporary alias to a column or table for the duration of a query. This alias appears in the result set header and can be referenced elsewhere in the query (e.g., ORDER BY).
Is AS required, or can I skip it?: AS is optional in most databases. Writing SUM(Sales) TotalSales is equivalent to SUM(Sales) AS TotalSales. Including AS is considered best practice for readability.
Can column aliases created with AS be used in WHERE?: Not in most databases, because WHERE is evaluated before SELECT. Instead, use the alias in ORDER BY or wrap the query in a subquery to filter by the alias.
Can I use spaces in an alias defined with AS?: Yes, but the alias must be enclosed in double quotes: SUM(Sales) AS "Total Sales". Without quotes, spaces will cause a syntax error.

Next: SQL SELECT UNIQUE

This page was last updated on March 19, 2026.

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SQL AS

Syntax

Example

Frequently Asked Questions

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