Re: (repost) Help understanding expressions in order by clause

Steve Midgley <public@misuse.org> writes:
> select * from test_order
> order by id <> 3, email
> --sql end

> Putting the expression "id <> 3" causes the id of 3 to sort to the TOP 
> of the list. This statement does the same thing:

> select * from test_order
> order by id = 3 DESC, email

> I know there is a good, rational reason for this, and I'm hoping 
> someone will explain it to me?

These expressions yield boolean true or false, and false sorts before true.
        regards, tom lane