Judge this month
substr(date,1,7)=to_char(last_day(to_date('2019-04-25','yyyy-mm-dd')), 'yyyy-mm')
Previous month (including this month)
substr(date,1,INSTR(date,' ')-1) <= to_char(last_day(to_date('2019-04-25','yyyy-mm-dd')), 'yyyy-mm-dd')
Judge this month
substr(date,1,7)=to_char(last_day(to_date('2019-04-25','yyyy-mm-dd')), 'yyyy-mm')
Previous month (including this month)
substr(date,1,INSTR(date,' ')-1) <= to_char(last_day(to_date('2019-04-25','yyyy-mm-dd')), 'yyyy-mm-dd')