Re: Lag and lead window functions order by weirdness

I've had a look at examples of lag and lead window functions with order by inside the OVER clause, and I'm confused as to why it influences the overall order in the output.

For example (for a table called category with incrementing id numbers up to 26):

SELECT id, lag(id) OVER (ORDER BY id DESC) FROM category;

This would yield:

id   lag

26   NULL

25   26

24   25

This is the equivalent of what we would get with:

SELECT id, lead(id) OVER (ORDER BY id ASC) FROM category ORDER BY id DESC;

I would expect the row order in the results not to be influenced by the OVER clause's ORDER BY as I thought that was just to determine how the aggregate window function's values would be output.  It's almost as if the main part of the query has inherited it's order from the OVER clause.

Am I missing something here?

Thanks

Thom