SQL Keyword - AS

AS Keyword

The AS keyword is used to give an alias or change the name of a table or column on a temporary basis.

This means an alias only exists for the duration of the query.

For example, you have a column named "Emp_Dept" but you want to show it as "Employee Department". So, using an alias, we can achieve it.

Alias For Column

When we want to change the name of a column, you can achieve it using the following syntax.

Syntax

SELECT <COLUMN_NAME> AS <NEW_NAME>, <COLUMN_NAME> AS <NEW_NAME> FROM <TABLE>;

Example 1

SELECT Emp_ID AS ID, Emp_Name AS Name FROM Employee;

Example 2 

If your alias name contains space or any reserved word in SQL, you must give it brackets or double quotes.

SELECT Emp_Name AS Name, Emp_Dept AS [Department Name] FROM Employee;

Example 3

SELECT Emp_Name, Add1 + ', ' + Add2 + ' ' + City + ', ' + Pincode AS Address FROM Employee;

Alias For Table

Sometimes we have to get the data from multiple tables, so if the column names are the same in multiple tables, at that time you have to specify the table name or alias name.

When we want to change the name of a table, you can achieve it using the following syntax.

Syntax

SELECT <TABLE_ALIAS>.<COLUMN_NAME_1>, <TABLE_ALIAS>.<COLUMN_NAME_2> FROM <TABLE_NAME> AS <TABLE_ALIAS>;

Example1

SELECT E.Emp_ID,E.Emp_Name From Employee AS E

Example2

SELECT E.Emp_ID,E.Emp_Name,D.Dept_Name,D.Dept_Id From Employee AS E
Join Department AS D On D.Dept_Id = E.Dept_Id

Summary

The As keyword is used as an alias. It is used to rename a column or a table.

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