Alias Name

An alias in SQL is a temporary name assigned to a table or a column for the duration of a query. It is mainly used to make column or table names easier to read and refer to, especially in complex queries involving joins, subqueries, or calculations.

Syntax:

• Column Alias:

SELECT column_name AS alias_name
FROM table_name;

(The AS keyword is optional.)

• Table Alias:

SELECT column_name
FROM table_name AS alias_name;

Column Alias Example:

Example 1: Simple Column Alias

You can use an alias to rename a column in the result set.

SELECT FirstName AS First, LastName AS Last
FROM Employees;

Result:

Here, FirstName is aliased as First, and LastName is aliased as Last in the query result, making the output more readable.

Table Alias Example:

Example 2: Table Alias for Simplicity

Table aliases are especially useful in queries with joins or self-joins.

SELECT E.FirstName, D.DepartmentName
FROM Employees AS E
JOIN Departments AS D ON E.DepartmentID = D.DepartmentID;

In this query:

• The alias E is used for the Employees table.
• The alias D is used for the Departments table.

Instead of repeating the full table names Employees and Departments throughout the query, the aliases E and D make the query easier to read and write.