oracle中如何將年周例如1502轉換為年月日20150105？

思路：先獲取年份和周數，然后獲取該年第一天是周幾， 然后獲取該年第一周的開始時間，然后加上（周數-1）*7，例子

with tmp as (select '1502' as a from dual union all select '1503' as a from dual union all select '1402' as a from dual union all select '0701' as a from dual)select a, to_char(years - w + (weeks - 1) * 7,'yyyymmdd') as begin_week from (select a, years, weeks, --因為oracle 的周是從周日開始,星期一是2 to_char(years, 'd') - 2 as w from (select a, to_date('20' || substr(a, 1, 2) || '-01-01', 'yyyy-mm-dd') as years, substr(a, -2, 2) as weeks from tmp))