>>>I have a log table with 4000 rows, each with a datetime stamp of when an action occured. I am trying to do a "date diff" between each row, and only show those rows that have taken longer than n seconds. I'm trying to get away from doing a table scan, does anyone have any help for doing it with pure SQL?
>>
>>

select * ;
>>from logtable lt ;
>>where lt.timestamp-lnGap > ;
>>(select max(timestamp) from logtable where timestamp < lt.timestamp)

>
>Thanks! I now want to add another column, which shows how long it actually took. How can I add that calculated column?

I can't think of a way of doing this without an UDF (UPDATE does not allow sub-queries):

update logtable set gap = findgap(timestamp)

function findgap
lparameters tm
local array laQry(1)

select max(timestamp) from logtable where timestamp < tm into array laQry
if empty(laQry(1))
	laQry(1) = tm
endif

return tm-laQry(1)