TableExpression permitting individual tables in the SELECT
statement to be "renamed" via the AS clause.
This may be necessary
for example, in cases where a table is joined to itself. The optional
column names in the FROM clause can be used to rename columns; this
renaming doesn't affect the names of the columns in the final result
set, but rather may be used to disambiguate column names in the
WHERE clause.
author: Stan Bailes