Oracle - 为日历日期的周数分配周一至周日周

Question

I have the data from 01 Jan 2019 - Present. I want to assign week numbers to the date column. The week should start on Monday and end on Sunday.

But the function I use starts from 01 Jan 2019 (Tuesday) as week 1 start date for the following to_number(to_char(to_date(CALENDAR_D, 'dd-mm-yyyy'), 'ww'))

If I replace 'ww' with 'iw', then it starts with first thursday of the week.

I want the cycle to be Monday to Sunday with the first monday of the year 2019 to be my first day of my first week.

Expected Output

Calendar_d       Week Number
01/01/2019        Any Number (Tuesday)
01/02/2019        Any Number
01/03/2019        Any Number
01/04/2019        Any Number
01/05/2019        Any Number
01/06/2019        Any Number (Sunday)
01/07/2019            1
01/08/2019            1
01/09/2019            1
01/10/2019            1
01/11/2019            1
01/12/2019            1
01/13/2019            1
01/14/2019            2

Answer 1

You can use next_day() and date arithmetic:

select floor((datecol - next_day(date '2019-01-01', 'Monday')) / 7) + 1 as weeknum

Or, if this is in a table, you can use window functions:

select t.datecol,
       sum(case when to_char(datecol, 'DY') = 'MON' then 1 else 0 end) over (partition by to_char(datecol, 'YYYY') order by t.datecol) as weeknum
from t
where t.datecol >= date '2019-01-01'