Re: obtain the difference between successive rows

"Raymond O'Donnell" <rod@iol.ie> writes:
> On 20/10/2012 17:23, Tom Lane wrote:
>> FWIW, Postgres is reasonably smart about the case of multiple window
>> functions with identical window definitions --- once you've got one
>> lag() in the query, adding more isn't going to cost much.

> Out of curiosity, would there be much difference between having multiple
> lag()s in the SELECT and a single one in a CTE?

Not sure what you're proposing?  I don't see how you'd solve this
problem with a CTE, at least not without a join, which seems unlikely
to be a win.

            regards, tom lane