how to convert date format in sql - sql

Question

if i have dates/time like these
8/5/2014 12:00:01 AM
8/5/2014 12:00:16 AM
8/5/2014 12:00:18 AM
8/5/2014 12:17:18 AM
8/5/2014 12:19:18 AM
i want these date/times
if the minutes less than 15 and greater than 00 i want the time for minutes to be 00
if the minutes less than 30 and greater than 15 i want the minutes to be 15
if the minutes less than 45 and greater than 30 i want the minutes to be 30
if the minutes less than 00 and greater than 45 i want the minutes to be 45
8/5/2014 12:00:00 AM
...
...
8/5/2014 12:15:00AM
...
...
8/5/2014 12:30:00AM
...
...
8/5/2014 12:45:00AM
i need to do that for my report
how can i apply these in oracle

Answer 1

Here's another method, which is really a variation of Gordon Linoff's approach:
trunc(dt, 'HH24') + ((15/1440) * (floor(to_number(to_char(dt, 'MI'))/15)))
The trunc(dt, 'HH24') gives you the value truncated to hour precision, so for your sample that's always midnight. Then floor(to_number(to_char(dt, 'MI'))/15) gives you the number of complete 15-minute periods represented by the minute value; with your data that's either zero or 1. As Gordon mentioned when you add a numeric value to a date it's treated as fractions of a day, so that needs to be multiplied by '15 minutes' (15/1400).
with t as (
select to_date('8/5/2014 12:00:01 AM') as dt from dual
union all select to_date('8/5/2014 12:00:16 AM') as dt from dual
union all select to_date('8/5/2014 12:00:18 AM') as dt from dual
union all select to_date('8/5/2014 12:17:18 AM') as dt from dual
union all select to_date('8/5/2014 12:19:18 AM') as dt from dual
union all select to_date('8/5/2014 12:37:37 AM') as dt from dual
union all select to_date('8/5/2014 12:51:51 AM') as dt from dual
)
select dt, trunc(dt, 'HH24')
+ ((15/1440) * (floor(to_number(to_char(dt, 'MI'))/15))) as new_dt
from t;
DT NEW_DT
---------------------- ----------------------
08/05/2014 12:00:01 AM 08/05/2014 12:00:00 AM
08/05/2014 12:00:16 AM 08/05/2014 12:00:00 AM
08/05/2014 12:00:18 AM 08/05/2014 12:00:00 AM
08/05/2014 12:17:18 AM 08/05/2014 12:15:00 AM
08/05/2014 12:19:18 AM 08/05/2014 12:15:00 AM
08/05/2014 12:37:37 AM 08/05/2014 12:30:00 AM
08/05/2014 12:51:51 AM 08/05/2014 12:45:00 AM

Answer 2

To add yet another method this looks like a situation where the function NUMTODSINTERVAL() could be useful - it makes it slightly more obvious what's happening:
select trunc(dt)
+ numtodsinterval(trunc(to_char(dt, 'sssss') / 900) * 15, 'MINUTE')
from ...
TRUNC() truncates the date to the beginning of that day. The format model sssss calculates the number of seconds since midnight. The number of complete quarter-hours since midnight is the number of seconds divided by 900 (as there are 900 quarter-hours in the day). This is truncated again to remove any part-completed quarter-hours, multipled by 15 to give the number of minutes (there are 15 minutes in a quarter hour). Lastly, convert this to an INTERVAL DAY TO SECOND and add to the original date.
SQL> alter session set nls_date_format = 'dd/mm/yyyy hh24:mi:ss';
Session altered.
SQL> with t as (
2 select to_date('05/08/2014 12:00:01') as dt from dual union all
3 select to_date('05/08/2014 12:00:16') as dt from dual union all
4 select to_date('05/08/2014 12:00:18') as dt from dual union all
5 select to_date('05/08/2014 12:17:18') as dt from dual union all
6 select to_date('05/08/2014 12:19:18') as dt from dual union all
7 select to_date('05/08/2014 12:37:37') as dt from dual union all
8 select to_date('05/08/2014 12:51:51') as dt from dual
9 )
10 select trunc(dt)
11 + numtodsinterval(trunc(to_char(dt, 'sssss') / 900) * 15, 'MINUTE')
12 from t
13 ;
TRUNC(DT)+NUMTODSIN
-------------------
05/08/2014 12:00:00
05/08/2014 12:00:00
05/08/2014 12:00:00
05/08/2014 12:15:00
05/08/2014 12:15:00
05/08/2014 12:30:00
05/08/2014 12:45:00
7 rows selected.
I've explicitly set my NLS_DATE_FORMAT so I can rely on implicit conversion in TO_DATE() so that it fits on the page without scrolling. It is not recommended to use implicit conversion normally.

Answer 3

Here is one method. Extract the date and then add in what you want as hours and minutes:
select trunc(dt) + extract(hour from dt) / 24.0 +
(trunc(extract(minute from dt) / 15) * 15) / (24.0 * 60);
This uses the fact that + for dates adds a number of days. The three terms are the original date at midnight, the number of hours converted to days (hence the / 24) and the third is the number of minutes, suitably rounded.

Answer 4

Here is an example for ORACLE with actual date:
select trunc(sysdate,'HH')+trunc(to_number(to_char(sysdate,'MI'))/15)*15/24/60
from dual;