Re: generate_series with left join - Mailing list pgsql-sql
| From | Aaron Bono |
|---|---|
| Subject | Re: generate_series with left join |
| Date | |
| Msg-id | bf05e51c0606281134s57ad9b37nd1991ad7c8928dd6@mail.gmail.com Whole thread Raw |
| In response to | generate_series with left join ("Pedro B." <pedro.borracha@msglab.com>) |
| Responses |
Re: generate_series with left join
|
| List | pgsql-sql |
How about one of these two:
select
year_list.year,
count(one.*),
count(two.*)
from (
select years
from generate_series(2006,2009) as years
) year_list
left outer join mytable as one on (
date_part('year', one.date) = year_list.years
and one.cause = 1
)
left outer join mytable as two on (
date_part('year', two.date) = year_list.years
and two.cause = 2
)
group by
year_list.year
;
select
year_list.year,
mytable.cause,
count(mytable.*)
from (
select years
from generate_series(2006,2009) as years
) year_list
left outer join mytable on (
date_part('year', mytable.date) = year_list.years
)
group by
year_list.year,
mytable.cause
;
I think one of the problems many people have is the writing of their SQL in paragraph form. It makes the SQL really hard to read and even harder to understand and debug. Formatting your SQL like I did above may make it easier to see what is wrong.
-Aaron Bono
select
year_list.year,
count(one.*),
count(two.*)
from (
select years
from generate_series(2006,2009) as years
) year_list
left outer join mytable as one on (
date_part('year', one.date) = year_list.years
and one.cause = 1
)
left outer join mytable as two on (
date_part('year', two.date) = year_list.years
and two.cause = 2
)
group by
year_list.year
;
select
year_list.year,
mytable.cause,
count(mytable.*)
from (
select years
from generate_series(2006,2009) as years
) year_list
left outer join mytable on (
date_part('year', mytable.date) = year_list.years
)
group by
year_list.year,
mytable.cause
;
I think one of the problems many people have is the writing of their SQL in paragraph form. It makes the SQL really hard to read and even harder to understand and debug. Formatting your SQL like I did above may make it easier to see what is wrong.
-Aaron Bono
On 6/28/06, Pedro B. <pedro.borracha@msglab.com> wrote:
Greetings.
I'm having some difficulties with my first use of the generate_series
function.
Situation:
cause | integer
date | timestamp(2) without time zone
cause | date
------+------------+-----------+
1 | 2006-03-23 15:07:53.63 |
2 | 2006-02-02 12:13:23.11 |
2 | 2006-11-12 16:43:11.45 |
1 | 2005-03-13 18:34:44.13 |
3 | 2006-01-23 11:24:41.31 |
(etc)
What i need to do, is to count the 'cause' column for the values '1' and
'2', and group them by year, using left joins in order to also have the
serialized years with empty values in the output.
My needed output for a series of (2005,2007) would be:
year | one | two
------+------+------
2005 | 1 | 0
2006 | 1 | 2
2007 | 0 | 0
I have tried something like
#select s, (select count(cause) from mytable where cause=1 ) as one,
COUNT (cause) as two from generate_series(2006,2009) AS s(d) left JOIN
mytable o ON (substr(o.date,1,4) = s.d and cause=2) GROUP BY s.d ORDER
BY 1;
which obviously is wrong, because of the results:
s | one | two
------+------+------
2006 | 3769 | 1658
2007 | 3769 | 0
2008 | 3769 | 0
2009 | 3769 | 0
As far as the 'two', the left join was successful, however i can not
find a way to join the 'one'. The output value is correct, but the
result shown should be only for the year 2006, not for all the values of
the series.
Maybe i've looked at it TOO much or maybe i'm completely failing to find
a working logic.
Any suggestions?
Any and all help is humbly appreciated.
\\pb