如何使用Oracle SQL获取sysdate月份中的所有日期？

Question

I try to get a query without parameters to obtain the list of dates from the current month.

Something like this:

SYSDATE = 16/07/15

I want the next list:

01/07/15
02/07/15
...
30/07/15
31/07/15

Answer 1

Selects all the days for current month

SELECT  TO_CHAR (TRUNC (SYSDATE, 'MM'), 'YYYYMMDD')+(LEVEL - 1) each_date
FROM    DUAL a
CONNECT BY LEVEL < (TO_NUMBER (TO_CHAR (TRUNC (SYSDATE, 'MM') - 1, 'DD'))+1)

Answer 2

Here's what I got to work:

SELECT TRUNC(SYSDATE, 'MM') + LEVEL - 1 AS day
FROM dual
CONNECT BY TRUNC(TRUNC(SYSDATE, 'MM') + LEVEL - 1, 'MM') = TRUNC(SYSDATE, 'MM')
;

The key in this query is TRUNC(SYSDATE, 'MONTH') which is the first day of the current month.
We use hierarchical queries to keep adding one day to the first day of the month until the value is no longer in the current month.
We use LEVEL - 1 because LEVEL starts from 1 and we need it to start from zero.

Here's a pseudo-query for what the above query does:

SELECT (start_of_month + days) AS day
FROM dual
WHILE MONTH_OF(start_of_month + days) = current_month

---

This query be a bit easier to understand:

SELECT *
FROM
(
    SELECT TRUNC(SYSDATE, 'MM') + LEVEL - 1 AS day
    FROM dual
    CONNECT BY LEVEL <= 32
)
WHERE EXTRACT(MONTH FROM day) = EXTRACT(MONTH FROM SYSDATE)

Answer 3

This should work:

    select trunc(sysdate, 'MONTH') + rownum - 1
      from dual
connect by rownum <= to_number(to_char(last_day(sysdate), 'DD'));

Answer 4

This is a trick using connect by. I truncate the date at the month level, effectively setting it to the 1st day of the month, add a day for each "level" and then filter for any day that occurs outside the month.

select day_of_month
from
(select (level - 1) + trunc(to_date('07/16/2015','MM/DD/YYYY'),'MM') day_of_month
from
dual
connect by level <= 31)
where day_of_month < add_months(trunc(to_date('07/16/2015','MM/DD/YYYY'),'MM'),1);