How do i convert a portion of day into a time?

Question

How do i convert a portion of day into a time, without dividing and modding the number myself?
For example, i calculated solar noon UTC to be .733409047. Adding that to the date gives the correct answer:
SQL> SELECT TO_DATE('1/1/2012', 'DD/MM/YYYY') + .733409047 FROM Dual;
TO_DATE('1/1/2012',
01/01/2012 17:36:07
A few questions, to actually understand this.
Is .733409047 implicitly converted? If so, to what datatype?
If i want HH:MM:SS does it need to be converted to a date, and then TO_CHAR? Or can the decimal be directly converted?
I'm currently trying to understand INTERVAL.
SQL> select interval '.5' day from dual;
select interval '.5' day from dual
ERROR at line 1:
ORA-01867: the interval is invalid
So, i'm obviously misunderstanding it. Can it be used here?

Answer 1

Hi,
Brian Tkatch wrote:
How do i convert a portion of day into a time, without dividing and modding the number myself?
For example, i calculated solar noon UTC to be .733409047. Adding that to the date gives the correct answer:
SQL> SELECT TO_DATE('1/1/2012', 'DD/MM/YYYY') + .733409047 FROM Dual;
TO_DATE('1/1/2012',
01/01/2012 17:36:07
A few questions, to actually understand this.
Is .733409047 implicitly converted? If so, to what datatype?No, there is no conversion going on here, just Date Arithmetic .
In Oracle, if d is a DATE and n is a NUMBER (not necessarily an integer, and not necessarily positive), d+n is the DATE that is n days later than d.
If i want HH:MM:SS does it need to be converted to a date, and then TO_CHAR? Or can the decimal be directly converted?Sorry, I don't understand. Are you saying that you want to do something like date arithmetic, but instead of using a number like .733409047 (meaning about .73 of a day), you want to pass a string like '17:36:07' (meaning 17 hours, 36 minutes and 7 seconds)? If so, INTERVAL DAY TO SECOND is probably your best bet. (It looks like you're already thinking along these lines.)
I'm currently trying to understand INTERVAL.
SQL> select interval '.5' day from dual;
select interval '.5' day from dual
ERROR at line 1:
ORA-01867: the interval is invalid
So, i'm obviously misunderstanding it. Can it be used here?You can only use integers like that. If you want to use any number, then use date arithmetic to add to (or subtract from) a DATE, or use NUMTIDSINTERVAL to produce an INTERVAL DAY TO SECOND:
SELECT     NUMTODSINTERVAL (.733409047, 'DAY')     AS intrvl
FROM     dual;Output:
INTRVL
+000000000 17:36:06.541660800 
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements), maybe about 5 rows, and also post the results you want from that data.
Explain, using specific examples, how you get those results from that data.
Always say which version of Oracle you're using.