使用add_months时在oracle中不是有效月份 [英] Not a valid month in oracle when add_months is used

问题描述

我在查询中给出了以下代码.

I have given the below code in query.

    where to_date(cal_wid,'yyyymmdd') 
    between  add_months(to_date(sysdate, 'MM-YYYY'),-12) 
    and      to_date(sysdate, 'MM-YYYY')

我遇到以下错误. (我正在Xampp服务器上做

I am getting the following bug. (I am doing in a Xampp server)

   Warning: oci_execute(): ORA-01843: not a valid month in C:\xampp\htdocs\xxx\index.php on line 149

   Warning: oci_fetch_array(): ORA-24374: define not done before fetch or execute and fetch in C:\xampp\htdocs\xxx\index.php on line 160

谁能告诉我为什么我会收到此错误?

Can anyone tell why I am getting this error?

推荐答案

永远不要在已经为DATE的对象上使用TO_DATE().这样做的原因是因为Oracle必须遵循您的意愿进行一些隐式转换:

Never, ever use TO_DATE() on something that is already a DATE. The reason for this is because Oracle will have to do some implicit conversions in order to follow your wishes:

TO_DATE(sysdate, 'mm-yyyy')

的运行方式实际上是

TO_DATE(TO_CHAR(sysdate, '<default nls_date_format parameter>'), 'mm-yyyy')

因此，如果您将nls_date_format设置为除'mm-yyyy'以外的其他值，您将会遇到问题.默认的nls_date_format参数为"DD-MON-YY"，比您设置的值大得多.

so if your nls_date_format is set to something that's other than 'mm-yyyy', you're going to have problems. The default nls_date_format parameter is 'DD-MON-YY', which is more than likely the value yours is set to.

如果您要做的只是将add_months添加到当前月份的第一天，则应使用TRUNC()，例如:

If all you wanted to do was to add_months to the 1st of the current month, then you should use TRUNC(), eg:

add_months(trunc(sysdate, 'MM'),-12)

如果您按照Lalit的要求对已经是日期的日期进行日期化，则这里证明了隐式to_char-涉及to_date(sysdate)的基本查询的执行计划:

Here's proof of the implicit to_char if you to_date something that's already a date, as requested by Lalit - an execution plan of a basic query involving to_date(sysdate):

SQL_ID  3vs3gzyx2gtcn, child number 0
-------------------------------------
select *  from   dual where  to_date(sysdate) < sysdate

Plan hash value: 3752461848

----------------------------------------------------------------------------
| Id  | Operation          | Name | E-Rows |E-Bytes| Cost (%CPU)| E-Time   |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |        |       |     2 (100)|          |
|*  1 |  FILTER            |      |        |       |            |          |
|   2 |   TABLE ACCESS FULL| DUAL |      1 |     2 |     2   (0)| 00:00:01 |
----------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter(TO_DATE(TO_CHAR(SYSDATE@!))<SYSDATE@!)

您可以清楚地看到TO_CHAR()在过滤条件下.

You can clearly see the TO_CHAR() in the filter condition.

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