The ordinal number refers to the position of the result column, counting from the left beginning at one. This makes it possible to order by a column that does not have a unique name. (You can assign a name to a result column using the AS clause.)
Vertica uses the ASCII collating sequence to store data and to compare character strings. In general the order is:
space
numbers
upper-case letters
lower-case letters
Special characters collate in between and after the groups mentioned. See man ascii for details.
For integer,bigint, and date/time data types, NULL appears first (smallest) in ascending order.
For float, boolean, char, and varchar, NULL appears last (largest) in ascending order.
