COLUMN ALIASING in Teradata

In addition to referring to a column by name, an alias or correlation name can be used.
Column aliases are used for join indexes when two columns have the same name.

Sample:
SELECT employee_name name, emp_id id
FROM tbl_employee

SELECT employee_name AS name, emp_id AS id
FROM tbl_employee

Note:
You can specify a column alias with or without the keyword AS.

Examples:
SELECT departnumber AS d, employeename e, salary
FROM personnel.employee
WHERE d IN(100, 500)
ORDER BY d, e ;