Obtain count to MI:SSSS precision? - oracle

Question

TRANSACTION_DATE is a DATE data type.
This code lists all of the event dates to the MI:SSSS.
select to_char(transaction_date,'YYYY-MON-DD HH24:MI:SSSS') as trans_date from ticket_orders;
Now I want to get counts for those dates and I get ORA-00979 not a GROUP BY function.
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');
ERROR ORA-00979: not a GROUP BY expression
How do I get a count of transactions to the MI:SSSS precision?

Answer 1

A DATE data type is a binary data type that is composed of 7 bytes representing century, year-of-century, month, day, hour, minute and second. It ALWAYS has those components and it NEVER contains fractional seconds (that is for the TIMESTAMP data type which can have fractional seconds and/or time zone information).
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
That is because you are displaying the seconds twice as you use the SS format model for seconds twice.
Your query can just be:
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

Answer 2

The DATE data type does not store fractional seconds. You can reference the 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.
If you want a data type that stores fractional seconds you will need to use 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.