我怎样才能得到从当天，当月或当年的第一天到当天的一周，一个月或一年的日期？

Question

I'm sorry if the title is confusing. Basically I am creating a dashboard using Oracle Apex 18.x and in one my card, I am comparing the sales between today vs yesterday, this week vs last week, this month vs last month and this year vs last year.

I have no problem with the today vs yesterday. My issue is with the week, month and year because I want to compare only up to the current day, not the whole last week.

For example, if today is the 4th day of the current week, then I'd have to compare it from last week up to its 4th day only as well.

For the month, if let's say today is 25-Mar-2018 then I should only compare it to the month of Feb from 1-25 only. Same with the year.

It wouldn't be a problem if the requirement is to get the full last week, full last month and full last year.

Answer 1

For week i would do it like:

select 
TRUNC(sysdate, 'DAY') start_of_the_week,
(sysdate) day_of_current_week,
(TRUNC(sysdate, 'DAY') - 7 ) start_of_last_week
(sysdate - 7) day_of_last_week,
from dual;

For month it would be:

select 
(sysdate) day_of_current_month,
TRUNC(sysdate, 'mm') month_start_date,
ADD_MONTHS(sysdate,-1) day_of_last_month,
ADD_MONTHS(TRUNC(sysdate, 'mm'),-1) start_of_last_month
from dual;