In response to Carel Combrink :
>
> They are not time stamped but in sequence. The latest active one is
> basically if you look at number 5. It goes from active to inactive to
> active again at time of the query. I want to know if the last entry of
> ID 5 was active or inactive. And so-forth for all the rest of the
> ID's. So only select the IDs that were active on their last entry into
> the database.
>
> Is there a way of querying the data to obtain only the last entry in
> the table for a given ID?
There are no UPDATE or DELETE, just only INSERTs into the table?
If yes, maybe this should work for you:
test=*# select * from test_select;
id | is_active
----+-----------
5 | t
5 | f
6 | t
7 | t
8 | t
5 | t
8 | f
9 | t
10 | t
6 | f
10 | f
(11 rows)
test=*# select id, is_active from (select id, is_active, max(ctid), row_number() over (partition by id) from
test_selectgroup by id, is_active, ctid order by id, ctid desc) foo where is_active and row_number = 1;
id | is_active
----+-----------
5 | t
7 | t
9 | t
(3 rows)
You *should* consider an additional column, timestamp for instance, the
trick with ctid isn't a clean solution.
Andreas
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Andreas Kretschmer
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