On 10/25/13, Robert James <srobertjames@xxxxxxxxx> wrote: > I have a table of (timed) events, and I'm interested in marking events > whose properties have changed from the previous event. > > I believe this can be done with window functions, but I'm not sure > how. What window function can give me a field from the _previous_ > row? > > (To elaborate, I'm interested in: > * Finding field x of the _previous_ row > * Finding field x of the _next_ row > * Finding field x of the _previous_ row that meets a certain criteria > (which the current row may or may not meet) > ) The first two are actually trivial - lag(field_x) over (order by [same order as query]) and lead(...). But the last one seems ellusive - How can I find the value of field x on the previous row WHERE a criteria is met? Is it possible to do this at all with a window function? -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
