SQL 按范围分组并保持 0

Question

我刚刚阅读了这个页面：In SQL, how can you "group by" in ranges?

回复对我有帮助，但我有一个问题，如果范围的 count() 等于 0，则范围不会显示，当 count() 等于 0 时如何显示范围？

这是我的查询：

select 
    w.Période, 
    nb from( select t.Période, count(*) as nb 
from (select 
          *, 
          case 
              when report.creation_date between '2017-05-28 00:00:00' and '2017-06-25 00:00:00' 
                  then 'P3' 
              when report.creation_date between '2017-06-25 00:00:00' and '2017-07-23 00:00:00' 
                  then 'P4' 
              when report.creation_date between '2017-07-23 00:00:00' and '2017-08-20 00:00:00' 
                  then 'P5' 
              when report.creation_date between '2017-08-20 00:00:00' and '2017-09-17 00:00:00' 
                  then 'P6' 
              else 'Avant' 
          end as Période 
      from report 
      where report.office_id = 11) as t 
      group by t.Période ) as w

这是我的结果：

Avant 57
P3 1
P5 2
P6 4

我想要：

Avant 57
P3 1
P4 0
P5 2
P6 4

我尝试过使用这些，但它不起作用。如果 count() 为 null 然后 0 else count() 以 nb 结束，或者当 count() = 0 then 0 else count() 以 nb 结束或 case when count() REGEXP '[^[:digit:]]' then 0 else count() end as nb

Answer 1

您应该将它们加入派生表：

SELECT t.period,
       COALESCE(s.nb,0) as yourCount
FROM(SELECT 'P1' as period 
     UNION ALL 
     SELECT 'P2' 
     UNION ALL 
     ...) t -- This is the derived table
LEFT JOIN(Your Query Here) s -- This is your query
 ON(t.period = s.period)

Answer 2

为了稍微清理一下 sagi 提供的内容，您需要额外的膨胀和分组，但需要对输出中所需的所有合格时段进行预查询...这将是您要查询的主表。然后，一个简单的 select from/group by 是 LEFT-JOIN

select 
     preQuery.Période, 
     coalesce( PreSum.AllRecs, 0 ) as TotalRecs
   from
      ( select 'P3' as Période
        union all select 'P4'
        union all select 'P5'
        union all select 'P6'
        union all select 'Avant' ) preQuery
         LEFT JOIN
         ( select 
                 case when r.creation_date between '2017-05-28 00:00:00' 
                                               and '2017-06-25 00:00:00' 
                      then 'P3'
                      when r.creation_date between '2017-06-25 00:00:00'
                                               and '2017-07-23 00:00:00' 
                      then 'P4' 
                      when r.creation_date between '2017-07-23 00:00:00'
                                               and '2017-08-20 00:00:00' 
                      then 'P5' 
                      when r.creation_date between '2017-08-20 00:00:00'
                                               and '2017-09-17 00:00:00' 
                      then 'P6' 
                      else 'Avant' 
                 end as Période,
                 count(*) as AllRecs
            from 
               report r
            where 
               r.office_id = 11
            group by
                 case when r.creation_date between '2017-05-28 00:00:00' 
                                               and '2017-06-25 00:00:00' 
                      then 'P3'
                      when r.creation_date between '2017-06-25 00:00:00'
                                               and '2017-07-23 00:00:00' 
                      then 'P4' 
                      when r.creation_date between '2017-07-23 00:00:00'
                                               and '2017-08-20 00:00:00' 
                      then 'P5' 
                      when r.creation_date between '2017-08-20 00:00:00'
                                               and '2017-09-17 00:00:00' 
                      then 'P6' 
                      else 'Avant' end ) PreSum
             on PreQuery.Période = PreSum.Période

Answer 3

如果您有表格中的值，但不是该办公室的值，您可以这样做：

  select (case when r.creation_date between '2017-05-28' and '2017-06-25' 
               then 'P3' 
               when r.creation_date between '2017-06-25' and '2017-07-23' 
               then 'P4' 
               when r.creation_date between '2017-07-23' and '2017-08-20' 
               then 'P5' 
               when r.creation_date between '2017-08-20' and '2017-09-17' 
               then 'P6' 
               else 'Avant' 
           end) as Période ,
          sum(r.office_id = 11) as cnt
  from report r
  group by Période;

条件聚合方法通常比使用外连接更容易实现。从显式选择所需行的意义上说，外连接更通用。这种方法更通用，因为它可以表示数据中的任何时期——即使它是一个新时期。

一些注意事项：

• 不需要这么多子查询。这只会使优化器的工作更难完成，并且人类更难以跟踪查询。
• 我非常喜欢限定列名（查询中的 r.s）。
• 指定日期时无需包含00:00:00。

事实上，更清晰的逻辑应该是：

如果您有表格中的值，但不是该办公室的值，您可以这样做：

  select (case when r.creation_date < '2017-06-26' 
               then 'P3' 
               when r.creation_date < '2017-07-24' 
               then 'P4' 
               when r.creation_date < '2017-08-21' 
               then 'P5' 
               when r.creation_date < '2017-09-18' 
               then 'P6' 
               else 'Avant' 
           end) as Période ,
          sum(r.office_id = 11) as cnt
  from report r
  where r.creation_date >= '2017-05-28'
  group by Période;

请注意，使用了不等式<。这很方便，因为它适用于日期和日期/时间。