如何使用互斥的 where 语句选择数据

Question

I want to execute a select statement based on a condition, change the where condition which are mutually exclusive

I want to get the data from a table based on the date. If the current date is 16th then i want the data for the dates 1-12 of the current month and if its 4th then i want the data for the previous whole month. I dont understand how to use if or when with this. How do i add a condition based on which i could execute one of the which statement. I am trying to automate a report that will run on the 16th and on the 4th of every month and the data that will be added to the report will be as explained before. I am using a oracle database

Answer 1

The logic would look like this using ANSI/ISO syntax:

where (extract(day from current_date) = 16 and
       extract(month from datecol) = extract(month from current_date) and extract(year from datecol) = extract(year from current_date)
      ) or
      (extract(day from current_date) = 4 and
       extract(month from datecol) = extract(month from current_date - interval '1 month') and extract(year from datecol) = extract(year from current_date - interval '1 month')
      )

Of course, date functions differ by database, so this might need to be adapted for your particular database.