Add Time value to a Date value

Question

Hi
COLUMN A is a DATE TYPE i.e. *14-MAR-13 12:30*
COLUMN B is a CHAR Type for hours and minutes: i.e. *01:45*.
I'm trying to sum (in SQL) the time in Col A with Col B, the result should be: 14:15
I'm not too sure how to proceed
THanks
Ruben

Answer 1

Ruben_920841 wrote:
Hi Frank,
Thank you for your quick reply.
However, I'm not sure I understand why you insert "TRUNC (b_date)" in your code below. Can you please explain?
>
WITH     got_b_date     AS
     SELECT     a, b
     ,     TO_DATE (b, 'HH24:MI')     AS b_date
     FROM     table_x
SELECT     a, b
,     a + ( b_date
     - TRUNC (b_date)
     )      AS a_plus_b
FROM table_x
>TO_DATE (b, 'HH24:MI') converts a string (such as '01:45') into a DATE (such as 1:45 AM on April 1, 2013). Since we're not passing a day of the month, month or year, those all take default values.
If d is a DATE, then TRUNC (d) is the earliest DATE (miodnight) on the same calendar day.
If d1 and d2 are DATEs, then d1 - d2 is the number of days (not necessarily an integer) that d1 is after d2.
If d is a DATE and n is a NUMBER (not necessarily an integer), then d + n is a DATE n days after d.
Put this all together and what do we have, given that b is '01:45'
b_date is 1:45 AM on some default day (for this solution, it doesn't matter which day)
TRUNC (b_date) is midnight on that same calendar day.
b_date - TRUNC (b_date) is a NUMBER, the number of days that 1:45 is after midnight (1:45 is 1.75 hours, and a day is 24 hours, so that comes to 1.75 / 24 = .072916666... days.)
a + (b_date - TRUNC (b_date)) is a DATE, .072916666... days (that is, 1.75 hours) after a.
Notice that Solomon did almost the same thing, only Solomon used the fact that the default day of the month in TO_DATE is 1, and that the default month and year are the same month and year that SYSDATE returns, so b_date - TRUNC (b_date) is the same as b_date - TRUNC (SYSDATE, 'MONTH').