On Wed, Jan 8, 2014 at 10:22 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Francisco Olarte <fola...@peoplecall.com> writes: > > Hi Nelson: > > On Wed, Jan 8, 2014 at 4:54 PM, Nelson Green <nelsongree...@gmail.com> > wrote: > >> I have a projects log table with a three column PK, project_num, > person_num, > >> and sequence, where each new entry for a project/person combination > >> increments the sequence, which is not an auto incrementing sequence. Is > >> there any way to retrieve the last entry to the table? For instance, if > the > >> last entry for person 427 on project 15 was sequence number 125, is that > >> information available to me anywhere? > > > SELECT MAX(sequence) FROM project_log_table WHERE person_num=427 AND > > project_num=15 > > Note that this will not work terribly well if there are concurrent > insertions for the same person/project. If that's not an issue, though, > it should be fine. It may be OK even if there are sometimes concurrent > insertions, if you are prepared to retry duplicate-key failures. > Concurrency is not likely to be an issue for this system, but I would certainly plan for it since I can not rule it out. > > > If it's a PK it should have an index and I believe it will be quite fast. > > It will be fast as long as sequence is the low-order column in the index. > > regards, tom lane >
