Oracle Get only time from To_Date() in a Query?

问题

I have an insert query:

INSERT INTO THE_TABLE (Field_A) 
VALUES (TO_DATE('08/12/2011 08:35:42 AM','HH:MI:SS PM'))
WHERE Something = 'SomethingElse'

Field_A is a Date field. When I execute the query, Field_A still shows a date and time.

Is there a way to grab only the time?

I have tried To_Char(), but then it converts to a string and the field wont take it.

I have also tried TO_DATE('08:35:42 AM','HH:MI:SS PM') and that doesn't work either, it still shows a date and time in the table.

回答1:

If your field is a date field, you will always have the date portion of your date time.

You could store it as something else, like just the number of seconds and use a conversion function to convert it to a time. Since it seems like TO_CHAR won't take a number and convert it a time, you'd have to do this on the application side.

So I'd just store it as a DATE anyways to avoid confusion; just ignore the date portion when using it.

And by the way, this:

I have tried To_Char(), but then it converts to a string and the field wont take it.

Is not quite right, because strings in the correct format are implicitly converted to DATEs.

回答2:

TO_DATE('08:35:42 AM','HH:MI:SS PM')

The reason this doesn't work is because this not a complete date. Even when you use a to_date('07/12/2011','MM/DD/YYYY'), Oracle stores the date and time, but makes all the components of the time ZERO. So the actual date stored is 07/12/2011 HH:MI:SS

If you want to store the time component seperately, It should be a varchar field and you'll need to add it to the date part to get the complete date. Example..

Select to_date(
          to_char(date_field_stored_as_date,'DD-MON-YYYY') || 
          ' ' ||
          to_char(time_field_stored_as_varchar),
         'DD-MON-YYYY HH24:MI:SS'    
       )

来源：https://stackoverflow.com/questions/7042230/oracle-get-only-time-from-to-date-in-a-query

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sql

Oracle

to-date