Re: Beginner Question...
От | Michael Wood |
---|---|
Тема | Re: Beginner Question... |
Дата | |
Msg-id | CAP6d-HUCS8DBsUbqpRuVK1xcZExJJez69zkVwGJToLASefngMw@mail.gmail.com обсуждение исходный текст |
Ответ на | Beginner Question... (James David Smith <james.david.smith@gmail.com>) |
Ответы |
Re: Beginner Question...
|
Список | pgsql-novice |
On 9 July 2011 18:41, James David Smith <james.david.smith@gmail.com> wrote: > Hi everyone, > > Could someone help me with this question please? I have a table with > four columns: > > - gps_id (primary key) > - date_time > - crimes_link (foreign key) > - osgb36_geom > > The data in the table involves lots of gps tracks of different > journeys. They are grouped into journeys by the 'crimes_link' field. > So for example the first 50 rows have an identical 'crimes_link' > field, then the next 50 rows a different value in 'crimes_link', then > the next 50 rows a different one, etc. What I would like to do is to > select the beginning location of each journey. This query gives me the > date_time of the beginning of the journey: > > SELECT crimes_link, MIN(date_time) > FROM camdengps3 > GROUP BY crimes_link; > > However I need to add the osgb36_geom column into the query and am unable too. > > Any ideas how to do this please? Sorry, I don't have time to test this now and maybe someone else has a better way, but maybe it will give you and idea: SELECT l.date_time, l.crimes_link, l.osgb36_geom FROM camdengps3 AS l INNER JOIN ( SELECT crimes_link, MIN(date_time) AS start FROM camdengps3 GROUP BY crimes_link) AS r ON l.date_time = s.start AND l.crimes_link = s.crimes_link; -- Michael Wood <esiotrot@gmail.com>
В списке pgsql-novice по дате отправления: