你可能最好将01到12存储在一个表中，但一般的方法是使用左连接：

Select
  m.Mo,
  Count(t.dateentered)
From (
    Select '01' As Mo From Dual Union All
    Select '02' From Dual Union All
    Select '03' From Dual Union All
    Select '04' From Dual Union All
    Select '05' From Dual Union All
    Select '06' From Dual Union All
    Select '07' From Dual Union All
    Select '08' From Dual Union All
    Select '09' From Dual Union All
    Select '10' From Dual Union All
    Select '11' From Dual Union All
    Select '12' From Dual
  ) m
    Left Outer Join
  mydatatable t
    On
      m.Mo = to_char(t.dateentered, 'MM') And 
      t.dateentered >= DATE'2011-01-01' And
      t.dateentered < DATE'2012-01-01'
Group By
  m.Mo
Order By
  m.Mo

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更新使用了一种更友好的索引方式来限制年份。
http://sqlfiddle.com/#!4/68085/10

您需要构建自己的12行月份“表”并执行左外连接。从您的问题中提取查询，并使其成为提供数据的内联视图。

SELECT m.month "Month", nvl(md.data, 0) "Count"
FROM
(
   select '01' month from dual union all
   select '02' month from dual union all
   select '03' month from dual union all
   select '04' month from dual union all
   select '05' month from dual union all
   select '06' month from dual union all
   select '07' month from dual union all
   select '08' month from dual union all
   select '09' month from dual union all
   select '10' month from dual union all
   select '11' month from dual union all
   select '12' month from dual
) m LEFT OUTER JOIN (
   /* Your Query Here */
) md ON m.month = md.month
ORDER BY m.month;

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结果应该是这样的：

Month       Count
------ ----------
01             32
02              0
03             12
04             11
05              0
06             10
07            222
08             32
09              0
10              0
11              0
12              0

型

您可以使用分层查询的connect by语法构建一个包含月份数字的虚拟表，然后左连接到您的数据：

with months as (
    select to_char(level, 'FM00') as month
    from dual
    connect by level <= 12
)
select m.month,
    count(mdt.rowid) as counter
from months m
left join mydatatable mdt
    on mdt.date_entered >= to_date('01/' || m.month || '/2011', 'DD/MM/YYYY')
    and mdt.date_entered <
        add_months(to_date('01/' || m.month || '/2011', 'DD/MM/YYYY'), 1)
group by m.month
order by m.month;

字符串
一些数据：

create table mydatatable (date_entered date, dummy number);
insert into mydatatable values (date '2011-06-02', 0);
insert into mydatatable values (date '2011-07-01', 0);
insert into mydatatable values (date '2011-10-01', 0);
insert into mydatatable values (date '2011-10-31', 0);
insert into mydatatable values (date '2011-11-01', 0);

型
...这给出：

MONTH COUNTER
----- -------
01          0 
02          0 
03          0 
04          0 
05          0 
06          1 
07          1 
08          0 
09          0 
10          2 
11          1 
12          0

型
或者SQL Fiddle，因为这似乎是这些天要做的事情...
通常最好避免类似to_char(date_entered, 'yyyy') = '2011'的东西，因为您将to_char()函数应用于表中的每一行，如果该列上有索引，则不会使用它。相反，尝试转换筛选器以匹配列的数据类型，如date_entered > date '2011-01-01' and date_entered < date '2012-01-01'。在这种情况下，它可以在连接条件中处理-我将每个月转换为2011年的日期范围，并且只在该月份范围内查找匹配的记录。

这很奇怪。。也许我误解了问题或数据...？在问题中添加表格和数据总是一个好主意。您应该通过计数获取所有月份的所有数据。我试过这个：

SELECT * FROM stack_test
/
CURR_MONTH  VAL
---------------
01          10
02          15
03          20
04  
05

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正如你所看到的，第4和第5个月没有值：

SELECT months, COUNT(rowid) counter 
   FROM
    (
     SELECT curr_month months
       FROM stack_test
    )
 GROUP BY months
 ORDER BY months
 /
 MONTHS COUNTER
 -------------------
 01           1
 02           1
 03           1
 04           1
 05           1

型
再举个例子：第2个月没有值，但我仍然可以计数。也许你需要总结一下你的价值观……：

SELECT mth, SUM(val) total_sum, Count(*) total_cnt 
  FROM 
  (
  SELECT mth, (CASE WHEN Mth = '01' THEN '10' ELSE '0' END) val
    FROM
    ( -- Annual table - replace 2 with 12 in Add_Months for the whole year -- 
     SELECT Trunc(SYSDATE,'Y')+Level-1 Curr_Year_By_Date
        , To_char(Trunc(SYSDATE, 'MM') + Rownum-1, 'MM' ) Mth
     FROM dual
    CONNECT BY Level <= Add_Months(Trunc(SYSDATE,'Y'),2)-Trunc(SYSDATE,'Y')
   )
  )
 GROUP BY mth
 ORDER BY 1
 /
 MTH    TOTAL_SUM   TOTAL_CNT
 -------------------------------------
 01         310         31
 02         0           28

型

这是我的示例，其中DAT_ULT_ALT类似于更新日期：
SELECT TO_CHAR（TMP_ULT_ALT，'YYYY-MM'）输入，计数（*）FROM表组输入顺序1