Re: obtain the difference between successive rows

On 20/10/2012 17:50, Tom Lane wrote:
> "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.

Yes, I see what you mean.... was waving my hands a bit. :-)

Ray.


--
Raymond O'Donnell :: Galway :: Ireland
rod@iol.ie