Thanks Craig, but I solved the issue by the below query :-
Here is the query for that :-
select bb_id,lat,lon,speed,dt_stamp from demo_table
inner join
(select bb_id as did, max(dt_stamp) as ts
from demo_table group by bb_id) as ds
on demo_table1.bb_id = ds.did and demo_table1.dt_stamp = ds.ts;
Best Regards
Adarsh
Adarsh Sharma wrote:
Any update on the below query :-
I tried the below query but :-
select bb_id,lat,lon,max(dt_stamp) from gps_tracker group by bb_id;
ERROR: column "gps_tracker.lat" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: select bb_id,lat,lon,max(dt_stamp) from gps_tracker group by...
^
********** Error **********
ERROR: column "gps_tracker.lat" must appear in the GROUP BY clause or be used in an aggregate function
SQL state: 42803
Character: 14
I think this can be solved by applying some function to lat lon values of max(dt_stamp) row.
Thanks
Adarsh Sharma wrote: Hi Craig :-
Below is the schema of my table :-
CREATE TABLE demo_table
(
id character varying NOT NULL,
lat double precision,
lon double precision,
speed double precision,
dt_stamp timestamp without time zone DEFAULT now(),
CONSTRAINT gps_tracker_pkey PRIMARY KEY (id)
)
WITH (
OIDS=FALSE);
I let u know after some work on Window functions
Thanks
Craig Ringer wrote:
On 10/10/2011 08:32 PM, Adarsh Sharma wrote:
Dear all,
I need to write a query to select latest rows with timestamp values.
My ID is repeated with lat lon and timestamp. I want the latest row of
each ID ( group by id ).
[snip]
"3911";"661000212";26.8491101532852;92.8058205131302;0;"2011-10-14
12:47:33.360572"
Can anyone let me know the query for that.
No, they can't. You only posted semicolon-separated data, not a schema with column names or anything much else.
For a task like this you can use a window function, or you can self-join and use a WHERE clause to match the greatest row. Using a window function will be MUCH more efficient, so only use the self-join if you're running on a really old version of PostgreSQL.
http://www.postgresql.org/docs/9.0/static/tutorial-window.html
http://www.postgresql.org/docs/9.0/static/functions-window.html
Using the first_value or last_value window functions with an ordering clause to select the greatest timestamp within each window frame.
http://www.postgresql.org/docs/9.0/static/functions-window.html#FUNCTIONS-WINDOW-TABLE
--
Craig Ringer
