Hi all, I'm trying to enumerate a list of months between a date in the past and
now and display a value from an existing table if there is one for the date or
NULL if there isn't.
I'm using this SQL to generate the months:
select distinct date_trunc( 'month', '2011-06-01'::date + tally_day )::date as
tally_mon
from generate_series( 0, ( select current_date - '2011-06-01'::date ) ) as
tally_day
[[ produces ]]
tally_mon
2011-06-01
2011-07-01
2011-08-01
2011-09-01
2011-10-01
(5 rows)
and I am trying to use it as the left hand side of a left join against my data
table:
select tally_table. tally_mon, met.datum
from (
select distinct date_trunc( 'month', '2011-06-01'::date + tally_day )::date
as tally_mon
from generate_series( 0, ( select current_date - '2011-06-01'::date ) ) as
tally_day
) as tally_table full outer join my_existing_table as met on( tally_mon =
met.month )
where met.series = 1;
-- ** See SETUP below **
This produces rows only for those that exist in my_existing_table and no left
join output which I'd expect for the rest of the tally_table rows.
What am I missing?
Many thanks,
Joel
SETUP:
create temp table my_existing_table ( month date not null, series int not null,
datum int not null );
insert into my_existing_table values ( '2011-08-01', 1, 5 ), ( '2011-10-01', 1,
4 );
--
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