Da du ikke har datoerne i tabellen, har du brug for en måde at generere dem på. Du kan bruge generate_series
funktion:
SELECT * FROM generate_series('2012-01-01'::timestamp, '2012-01-07 23:00', '1 hour') AS ts;
Dette vil give resultater som dette:
ts
---------------------
2012-01-01 00:00:00
2012-01-01 01:00:00
2012-01-01 02:00:00
2012-01-01 03:00:00
...
2012-01-07 21:00:00
2012-01-07 22:00:00
2012-01-07 23:00:00
(168 rows)
Den resterende opgave er at forbinde de to udvalgte ved hjælp af en ydre joinforbindelse som denne :
select extract ( day from ts ) as day, extract ( hour from ts ) as hour,coalesce(count,0) as count from
(
SELECT extract ( day from date ) as day , extract ( hour from date ) as hr ,count(*)
FROM sr
where date>'2012-01-01' and date <'2012-01-07'
GROUP BY extract ( day from date ) , extract ( hour from date )
) AS cnt
right outer join ( SELECT * FROM generate_series ( '2012-01-01'::timestamp, '2012-01-07 23:00', '1 hour') AS ts ) as dtetable on extract ( hour from ts ) = cnt.hr and extract ( day from ts ) = cnt.day
order by day,hour asc;