Previous Weekdays - sql

Question

I have a requirement in which i have to find start and end date.
Start date is First sat of the previous month of created date and end date is previous friday of created date.
Eg Below .. I am passing created date and need to derive start and end date like this below.
CREATED_DT Start_date end_date
04/08/2015 15:36 04/07/2015 00:00 31/07/2015 23:59
07/07/2015 15:32 06/06/2015 00:00 03/07/2015 23:59

Answer 1

You should not depend on the locale-specific NLS settings.
You could use following functions:
NEXT_DAY
ADD_MONTHS
TRUNC
For example,
SQL> alter session set nls_date_format='DD/MM/YYYY HH24:MI:SS';
SQL> WITH t(created_dt) AS(
2 SELECT to_date('04/08/2015 15:36','DD/MM/YYYY HH24:MI') FROM DUAL UNION ALL
3 SELECT to_date('07/07/2015 15:32','DD/MM/YYYY HH24:MI') FROM DUAL
4 )
5 SELECT CREATED_DT,
6 NEXT_DAY(TRUNC(add_months(created_dt, -1),'MM') -1,TO_CHAR(to_date('6','J'),'Day')) -1 start_date,
7 NEXT_DAY(TRUNC(created_dt, 'MM') -1, TO_CHAR(to_date('5','J'),'Day')) -1 + 0.99999 AS end_date
8 FROM t;
CREATED_DT START_DATE END_DATE
------------------- ------------------- -------------------
04/08/2015 15:36:00 04/07/2015 00:00:00 31/07/2015 23:59:59
07/07/2015 15:32:00 06/06/2015 00:00:00 03/07/2015 23:59:59
SQL>
To get the time portion as 23:59:59, you could either add 0.99999 or subtract INTERVAL '1' SECOND. For example,
SQL> alter session set nls_date_format='DD/MM/YYYY HH24:MI:SS';
Session altered.
SQL> WITH t(created_dt) AS(
2 SELECT to_date('04/08/2015 15:36','DD/MM/YYYY HH24:MI') FROM DUAL UNION ALL
3 SELECT to_date('07/07/2015 15:32','DD/MM/YYYY HH24:MI') FROM DUAL
4 )
5 SELECT CREATED_DT,
6 NEXT_DAY(TRUNC(add_months(created_dt, -1),'MM') -1,TO_CHAR(to_date('6','J'),'Day')) -1 start_date,
7 NEXT_DAY(TRUNC(created_dt, 'MM') -1, TO_CHAR(to_date('5','J'),'Day')) - (INTERVAL '1' SECOND) AS end_date
8 FROM t;
CREATED_DT START_DATE END_DATE
------------------- ------------------- -------------------
04/08/2015 15:36:00 04/07/2015 00:00:00 31/07/2015 23:59:59
07/07/2015 15:32:00 06/06/2015 00:00:00 03/07/2015 23:59:59
SQL>

Answer 2

You can use some of the Date functions. I'm giving for sysdate. Use according to your requirement.
select NEXT_DAY(trunc((trunc (add_months (sysdate, -1), 'mm')), 'MONTH')-1, 'Saturday') as Start_date,
NEXT_DAY(SYSDATE-8, 'FRIDAY') as End_date
from dual;
Output
START_DATE END_DATE
04-JUL-15 21-AUG-15

Answer 3

Use Next_day function. The Oracle/PLSQL NEXT_DAY function returns the first weekday that is greater than a date.
select TO_DATE('04/08/2015 15:36' ,'DD/MM/YYYY hh24:mi') as created_date,
next_day(ADD_MONTHS(TRUNC(TO_DATE('04/08/2015 15:36','DD/MM/YYYY hh24:mi')+1,'MM'),-1),'SATURDAY')
as start_date,
next_day(trunc(TO_DATE('04/08/2015 15:36','DD/MM/YYYY hh24:mi')-8)+0.99999 ,'FRIDAY')as end_date
FROM DUAL
Instead of adding 0.99999 we can also achieve same thing with 1-(1/(24*60*60)) we are adding one day after that subtracting 1 part from 24*60*60 seconds.

Answer 4

I have achieved by this way
end date: Where created _dt is date value what i am passing..!!
next_day(TRUNC(to_date(created_dt,'DD-MM-YYYY HH24:MI:SS'))-7,'FRIDAY') +
INTERVAL '23:59:59' HOUR TO SECOND AS range_end_dt