Where can I find more info about the UNIQUE (unique DESC) sql syntax?

[adriancuadrado]

I was reading this article when I stumbled upon this SQL:

CREATE TABLE `Unique` (
  `unique` INT,
  CONSTRAINT `Unique_unique_key` UNIQUE (`unique` DESC)
)

I didn't know you could specify (`unique` DESC), but when I went to do some research about it I couldn't find any documentation in Postgresql.