수요일을 기준으로 금주/전주의 기간을 구함

select  decode(to_char(to_date(:p_day), 'day'),
              '수요일', to_date(:p_day),
              next_day(to_date(:p_day), '수요일')) - 13 as p_week_start,
        decode(to_char(to_date(:p_day), 'day'),
              '수요일', to_date(:p_day),
              next_day(to_date(:p_day), '수요일')) - 7 as p_week_end,
        decode(to_char(to_date(:p_day), 'day'),
              '수요일', to_date(:p_day),
              next_day(to_date(:p_day), '수요일')) - 6 as c_week_start,
        decode(to_char(to_date(:p_day), 'day'),
              '수요일', to_date(:p_day),
              next_day(to_date(:p_day), '수요일')) as c_week_end
  from dual
;