Formatting INTERVAL DAY(0) TO SECOND(0)

问题

I have a few time fields that are INTERVAL DAY(0) TO SECOND(0) Datatypes to store various times of the day.

Currently on normal retrieval, my fields display as such:

+00 19:00:00.000000

How am I able to format this such that it displays as 19:00?

回答1:

You want hours and minutes from an interval. If that interval cannot exceed 24 hours, then you can add the interval to a date without time part and then use TO_CHAR to get the formatted hours and minutes:

select to_char(trunc(sysdate) + myinterval, 'hh24:mi') from mytable

If, however, the interval can be larger (e.g. 100 hours and 15 minutes: 100:15), then you'll need another approach:

select 
  to_char(extract (day from myinterval) * 24 + extract (hour from myinterval)) ||
  ':' ||
  to_char(extract (minute from myinterval), 'fm00')
from mytable

回答2:

In contradiction to documentation you cannot use function TO_CHAR() for intervals. It allows to use INTERVAL values but the result is always the same. On another place the documentation says:

Interval data types do not have format models.

You can use either EXTRACT() function or you can work with Regular Expressions:

WITH t AS 
    (SELECT INTERVAL '19' HOUR + INTERVAL '30' MINUTE AS i FROM dual)
SELECT 
    LPAD(EXTRACT(HOUR FROM i), 2, '0')||':'||LPAD(EXTRACT(MINUTE FROM i), 2, '0'),
    REGEXP_SUBSTR(i, '\d{2}:\d{2}')
FROM t;

Usually it is not very smart to use Regular Expression on date/time values. On the other hand, since format of INTERVAL does not depend on any NLS-Settings it is a feasible option.

Disadvantage of EXTRACT is when you have negative intervals. Such an interval would be written like -19:-30 because every component is returned with minus sign (-). Also be aware that EXTRACT returns NUMBER values, so you have to pad them with '0' manually.