Oracle SQL：データなしで空の週/週を表示するにはどうすればよいですか？

パーティション化された外部結合 を使用します ：

select data.id, weeks.weekend_day, nvl(value, 0) value
from
(
    select date '2012-01-01' weekend_day from dual union all
    select date '2012-01-08' weekend_day from dual union all
    select date '2012-01-15' weekend_day from dual
) weeks
left join
(
    select 'A00' id, date '2012-01-01' weekend_day, 1 value from dual union all
    select 'A00' id, date '2012-01-08' weekend_day, 7 value from dual union all
    select 'B00' id, date '2012-01-08' weekend_day, 4 value from dual union all
    select 'B00' id, date '2012-01-15' weekend_day, 3 value from dual
) data
    partition by (data.id)
    on weeks.weekend_day = data.weekend_day