SQL-填写没有结果的日期 [英] SQL -- Filling in Dates that don't have results

问题描述

我有这个查询:

Select Trunc(Create_Dtime),Count(Trunc(Create_Dtime)) as Day_0 From Player
Group By Trunc(Create_Dtime)
Order By Trunc(Create_Dtime) Asc

它给我回溯日期，但是如果一个日期没有任何结果，则将其跳过.我想填写从8-05-12到现在的所有日期，如果那几天没有任何值，则结果中应为0.

It gives me back dates but if a date doesn't have any results, that is skipped. I'd like to fill in all dates from 8-05-12 to present, and if those days don't have any values, just have a 0 in the results.

推荐答案

根据您要创建它们的方式，您可以创建 connect by 语法动态生成行

Depending on how you want to create them you can either create a calender table or generate the rows dynamically using the Oracle connect by syntax.

with the_dates as (
  select max(trunc(Create_Dtime)) as max_date
       , min(trunc(Create_Dtime)) as min_date
    from player 
         )
  , generator as (
  select min_date + level as the_date
    from the_dates
 connect by level <= max_date
         )
select g.the_date, count(trunc(p.Create_Dtime))
  from generator g
  left outer join player p
    on g.the_date = trunc(p.Create_Dtime)
 group by g.the_date
 order by g.the_date desc

如果您选择压光机表格"选项，它会更干净:

If you go down the calender table option it's a little bit cleaner:

with the_dates as (
  select max(trunc(Create_Dtime)) as max_date
       , min(trunc(Create_Dtime)) as min_date
    from player 
         )
select c.the_date, count(trunc(p.Create_Dtime))
  from calender c
  join the_dates td
    on c.the_date between td.min_date and td.max_date
  left outer join join player p
    on c.the_date = trunc(p.Create_Dtime)
 group by c.the_date
 order by c.the_date

或者，刚注意到您的日期限制:

Or, having just noticed your date constraints:

with the_dates as (
  select to_date('07-05-2012','dd-mm-yyyy') + level as the_date
    from dual
 connect by level <= trunc(to_date('07-05-2012','dd-mm-yyyy') - sysdate)
         )
 select td.the_date, count(trunc(p.create_dtime))
   from the_dates td
   left outer join player p
     on td.the_date = trunc(p.create_dtime)
  group by td.the_date
  order by td.the_date

对于所有这些，我建议在您的player表上的trunc(create_dtime)上建立一个索引.

For all of these I'd recommend an index on trunc(create_dtime) on your player table.

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