Oracle SQL - 根据当前月份定义日期的年元素

Question

I am trying to create a view in SQL Developer based on this statement:

SELECT * FROM ORDERS WHERE START_DATE > '01-JUL-2020'

The year element of the date needs to set to the year of the current date if the current month is between July and December otherwise it needs to be the previous year.

The statement below returns the required year but I don't know how to incorporate it (or a better alternative) into the statement above:

select
    case
      when month(sysdate) > 6 then 
        year(sysdate)
      else
        year(sysdate)-1
    end year
  from dual

Thanks

Answer 1

Oracle doesn't have a built-in month function so I'm assuming that is a user-defined function that you've created. Assuming that's the case, it sounds like you want

where start_date > (case when month(sysdate) > 6
                         then trunc(sysdate,'yyyy') + interval '6' month
                         else trunc(sysdate,'yyyy') - interval '6' month
                      end)

Answer 2

Just subtract six months and compare the dates:

SELECT *
FROM ORDERS
WHERE trunc(add_months(sysdate, -6), 'YYYY') = trunc(start_date, 'YYYY')

This compares the year of the date six months ago to the year on the record -- which seems to be the logic you want.