Aliases: AS

Aliases can be used for column names and table names. > SELECT column AS column_alias FROM table > SELECT column FROM table AS table_alias Example: > SELECT name AS "first name", id FROM stud; first name | id ------------+---- fred | 1 tom | 3 john | 4 lisa | 2 (4 rows) With table aliases, you can join a table to itself in a self-join.
In this case, the same table is given two different alias names.