获取 MI:SSSS 精度的计数？

Question

TRANSACTION_DATE 是 DATE 数据类型。

此代码列出了 MI:SSSS 的所有事件日期。

select to_char(transaction_date,'YYYY-MON-DD HH24:MI:SSSS') as trans_date from ticket_orders;

现在我想获取这些日期的计数，但我得到的是 ORA-00979 而不是 GROUP BY 函数。

    select to_char(transaction_date,'YYYY-MON-DD HH24:MI:SSSS') as trans_date,
     count(*)
      from ticket_orders
       group by to_char(transaction_date,'YYYY-MON-DD HH24:MI:SSSS');

错误 ORA-00979: not a GROUP BY expression

如何获得 MI:SSSS 精度的交易计数？

Answer 1

DATE 数据类型不存储小数秒。您可以参考Oracle documentation about data types.

DATE

Valid date range from January 1, 4712 BC, to December 31, 9999 AD. The default format is determined explicitly by the NLS_DATE_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is fixed at 7 bytes. This data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND. It does not have fractional seconds or a time zone.

如果您想要存储小数秒的数据类型，则需要使用 TIMESTAMP

TIMESTAMP [(fractional_seconds_precision)]

Year, month, and day values of date, as well as hour, minute, and second values of time, where fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values of fractional_seconds_precision are 0 to 9. The default is 6. The default format is determined explicitly by the NLS_TIMESTAMP_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is 7 or 11 bytes, depending on the precision. This data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND. It contains fractional seconds but does not have a time zone.

Answer 2

一种DATE数据类型是一种二进制数据类型，由7个字节组成，分别代表世纪、year-of-century、月、日、时、分、秒。它 ALWAYS 具有这些组件，它 NEVER 包含小数秒（即 TIMESTAMP 数据类型可以有小数秒 and/or时区信息).

If DATE type does not store fractional seconds, why does a typical row from my first query look like this 2021-FEB-25 07:58:2626

那是因为您两次使用 SS 格式模型显示秒数。

您的查询可以是：

select to_char(transaction_date,'YYYY-MON-DD HH24:MI:SS') as trans_date,
       count(*)
from   ticket_orders
group by
       transaction_date;

db<>fiddle here

获取 MI:SSSS 精度的计数？

Obtain count to MI:SSSS precision?

oracle

date

plsql

oracle12c