Insert weekly dates starting fridays - sql

Question

I'm trying to insert weekly dates in my table, the start date is always on Fridays and the end date is always on thursday. I'm using this code :
CREATE TABLE WEEK AS
WITH generator AS (
SELECT DATE '2015-01-02' + LEVEL - 1 dt
FROM dual
CONNECT BY LEVEL <= DATE '2016-01-21' - DATE '2015-01-02' + 1
)
SELECT to_char(dt, 'YYYY "SEM"IW') "KEY",
dt "DATE_START",
least(next_day(dt - 1, to_char(DATE '2015-01-08', 'DAY')),
last_day(dt)) "DATE_END"
FROM generator
WHERE to_char(dt, 'D') = to_char(DATE '2015-01-02', 'D');
The code is working for weeks on the same month, but if I have a starting date on a month and the finish date on the next month, there's no data inserting in my table.
For example :
Date_ START | DATE_END
29-05-2015 | 31-05-2015
05-06-2015 | 11-05-2015
Instead of 31-05-2015 I should have 04-06-2015.

Answer 1

I think the following is what you're after:
with generator as (select date '2015-05-29' + (level - 1)*7 dt
from dual
connect by level <= (date '2016-01-21' - date '2015-05-29')/7 + 1)
select to_char(dt, 'YYYY "SEM"IW') "KEY",
dt "DATE_START",
dt + 6 "DATE_END"
from generator;
KEY DATE_START DATE_END
---------- ---------- ----------
2015 SEM22 2015-05-29 2015-06-04
2015 SEM23 2015-06-05 2015-06-11
2015 SEM24 2015-06-12 2015-06-18
2015 SEM25 2015-06-19 2015-06-25
<snip>
2016 SEM01 2016-01-08 2016-01-14
2016 SEM02 2016-01-15 2016-01-21
This is assuming that the dates you have specified in the generator subquery have already been determined to be a Friday. Otherwise you could use something like trunc(<date> - 4, 'iw') + 4 or trunc(<date> + 3, 'iw') + 4 (depending on whether you want the previous or next Friday to be included for the date specified) to make sure that the seed date is definitely a Friday.

Answer 2

Maybe just an alternative you can try analytical function here. But as
suggested by Boniest "just adding days" will be better approach. Have
fun
WITH generator AS
(SELECT DATE '2015-01-02' + LEVEL - 1 dt
FROM dual
CONNECT BY LEVEL <= DATE '2016-01-21' - DATE '2015-01-02' + 1
)
-- select * from generator;
SELECT TO_CHAR(dt, 'YYYY "SEM"IW') "KEY",
dt "DATE_START",
lead(dt) over (ORDER BY (dt)) -1 "End Date"
FROM generator
WHERE TO_CHAR(dt, 'D') = TO_CHAR(DATE '2015-01-02', 'D');
----------------------------------OUTPUT-----------------------------------------
**KEY DATE_START End Date**
2015 SEM18 05/01/2015 05/07/2015
2015 SEM19 05/08/2015 05/14/2015
2015 SEM20 05/15/2015 05/21/2015
2015 SEM21 05/22/2015 05/28/2015
2015 SEM22 05/29/2015 06/04/2015
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