[英]Is it possible to construct a date out of the calendar week plus year in oracle?
I have a column containing calendar weeks plus year as string, which was constructed in way like this我有一个包含日历周加上年份作为字符串的列,它的构造方式是这样的
select TO_CHAR(TO_DATE('01.03.2020'),'WW/YYYY') from DUAL
which results in a string like这导致像这样的字符串
09/2020
Is it possible to reconstruct the date from this string?是否可以从此字符串重建日期? I would not care if the date is start of the week, end of the week or anything else within this week.
我不在乎日期是一周的开始,一周的结束还是本周内的其他任何事情。
The WW
format code counts 7-day periods starting at 1st January so just get 1st January for your year and add the correct number of 7-day periods: WW
格式代码从 1 月 1 日开始计算 7 天周期,因此只需为您的年份获取 1 月 1 日并添加正确数量的 7 天周期:
Oracle Setup :甲骨文设置:
CREATE TABLE table_name ( value ) AS
SELECT TO_CHAR( DATE '2020-03-01', 'WW/YYYY' ) FROM DUAL;
Query :查询:
SELECT TO_DATE( SUBSTR( value, 4 ), 'YYYY' ) + ( SUBSTR( value, 1, 2 ) - 1 ) * 7
AS first_day_of_week,
TO_DATE( SUBSTR( value, 4 ), 'YYYY' ) + ( SUBSTR( value, 1, 2 ) ) * 7 - 1
AS last_day_of_week
FROM table_name
Output :输出:
\nFIRST_DAY_OF_WEEK |FIRST_DAY_OF_WEEK | LAST_DAY_OF_WEEK
LAST_DAY_OF_WEEK\n:---------------- |
:---------------- | :---------------
:--------------\n2020-02-26 |
2020-02-26 | 2020-03-03
2020-03-03 \n
Something like this?像这样的东西?
with test (col) as
(select '09/2020' from dual),
-- construct the whole year with week markers
whole_year as
(select to_date(substr(col, -4), 'yyyy') + level - 1 datum,
--
to_char(to_date(substr(col, -4), 'yyyy') + level - 1, 'ww') week
from test
connect by level <= add_months(to_date(substr(col, -4), 'yyyy'), 12) -
to_date(substr(col, -4), 'yyyy')
)
select min(datum)
from whole_year
where week = '09';
The whole_year
CTE - for week 09 - looks like this: whole_year
CTE - 第 09 周 - 看起来像这样:
DATUM WE
---------- --
25.02.2020 08
26.02.2020 09 --> this
27.02.2020 09
28.02.2020 09
29.02.2020 09
01.03.2020 09
02.03.2020 09
03.03.2020 09
04.03.2020 10
05.03.2020 10
06.03.2020 10
which means that query I posted above, as a result, returns这意味着我在上面发布的查询结果返回
<snip>
12 select min(datum)
13 from whole_year
14 where week = '09';
MIN(DATUM)
----------
26.02.2020
SQL>
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