Question

我有一个表格，该表格由DATE列d_dly_label分区并编入索引。

我正试图了解这对max(d_dly_label)的影响。为什么它会为以下两个查询生成不同的值：

查询1：

select 
  max(d_dly_label) 
from 
  ECP.TSPT105
where 
  d_dly_label <= to_date('12/06/2015', 'dd/mm/yyyy');
--result: 13/JUL/14

查询2：

select 
  max(d_dly_label) 
from 
  ECP.TSPT105
where 
  d_dly_label <= to_date('12/06/2015', 'dd/mm/yyyy')
  and d_dly_label >= to_date('12/06/2015', 'dd/mm/yyyy') - 1;
--result: 11/JUN/15

如何将更多条件添加到where子句会导致更高 max(d_dly_label)？

更新：我从SQL Developer中获取了DDL并将其缩减为一个复制问题的简短示例。

drop table tmp_105_copy;

CREATE TABLE tmp_105_copy
(
  D_DLY_LABEL DATE NOT NULL 
)
PARTITION BY LIST (D_DLY_LABEL) 
(
  PARTITION JUL2014_13 VALUES (TO_DATE(' 2014-07-13 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')) 
  , PARTITION JUN2015_11 VALUES (TO_DATE(' 2015-06-11 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')) 
);

CREATE INDEX tmp_I1_TSPT105 ON tmp_105_copy(D_DLY_LABEL ASC) 
LOCAL 
(
  PARTITION JUL2014_13 
, PARTITION JUN2015_11 
);

insert into tmp_105_copy values (to_date('13jul2014','ddmonyyyy'));
insert into tmp_105_copy values (to_date('11jun2015','ddmonyyyy'));

commit;

select 
  max(d_dly_label) 
from 
  tmp_105_copy
where 
  d_dly_label <= to_date('12/06/2015', 'dd/mm/yyyy');
-- 13/JUL/14

analyze table tmp_105_copy estimate statistics;  

select 
  max(d_dly_label) 
from 
  tmp_105_copy
where 
  d_dly_label <= to_date('12/06/2015', 'dd/mm/yyyy');
-- still 13/JUL/14

select 
  max(d_dly_label) 
from 
  tmp_105_copy
where 
  d_dly_label <= to_date('12/06/2015', 'dd/mm/yyyy')
  and d_dly_label >= to_date('12/06/2015', 'dd/mm/yyyy') - 1;
--11/JUN/15

select 
  max(to_date(d_dly_label))
from 
  tmp_105_copy
where 
  d_dly_label <= to_date('12/06/2015', 'dd/mm/yyyy');
-- also 11/JUN/15

Answer 1

也许这是表格中的索引字段？如果统计数据错误，则可能会出现此类错误结果。您可以尝试更新表的统计信息并再次检查您的查询。

Oracle 10g - 使用max on date列，它既是分区又是索引

1 个答案: