If the AS clause is specified, the name of the result column is the name
specified on the AS clause.
If the AS clause is not specified and a column list is specified in the
correlation clause, the name of the result column is the corresponding name
in the correlation column list.
If neither an AS clause nor a column list in the correlation clause is
specified and the result column is derived only from a single column (without
any functions or operators), then the result column name is the unqualified
name of that column.
If neither an AS clause nor a column list in the correlation
clause is specified and the result column is derived only from a single variable
(without any functions or operators), then the result column name is the unqualified
name of that variable.