相关疑难解决方法(0)

我有不均匀分布的数据(wrt日期)几年(2003-2008).我想查询一组给定的开始和结束日期的数据,按PostgreSQL 8.3中任何支持的时间间隔(日,周,月,季,年)对数据进行分组(http://www.postgresql.org/docs /8.3/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC).

问题是某些查询会在所需的时间段内提供连续的结果,如下所示:

select to_char(date_trunc('month',date), 'YYYY-MM-DD'),count(distinct post_id) 
from some_table where category_id=1 and entity_id = 77  and entity2_id = 115 
and date <= '2008-12-06' and date >= '2007-12-01' group by 
date_trunc('month',date) order by date_trunc('month',date);
          to_char   | count 
        ------------+-------
         2007-12-01 |    64
         2008-01-01 |    31
         2008-02-01 |    14
         2008-03-01 |    21
         2008-04-01 |    28
         2008-05-01 |    44
         2008-06-01 |   100
         2008-07-01 |    72
         2008-08-01 |    91
         2008-09-01 |    92
         2008-10-01 |    79
         2008-11-01 |    65
        (12 rows)

但有些人因为没有数据而错过了一些间隔,因为这个:

select …