CREATE OR REPLACE FUNCTION f_week_to_date(a_week varchar2) RETURN CHAR IS
   v_first_date   char(10);
   v_date_of_week number(1);

BEGIN
select to_char(to_date(substr(a_week, 1, 4) || '0101', 'yyyymmdd'), 'D')
    into v_date_of_week
    from dual;
   v_date_of_week := v_date_of_week - 1;
   if v_date_of_week <= 4 then
    select TO_CHAR(TO_DATE(SUBSTR(a_week, 1, 4) || '0101', 'yyyymmdd') +
                    SUBSTR(a_week, 5, 2) * 7 - 7 - v_date_of_week + 1,
                   'yyyy-mm-dd')
      into v_first_date
      from dual;
else
    select TO_CHAR(TO_DATE(SUBSTR(a_week, 1, 4) || '0101', 'yyyymmdd') +
                    SUBSTR(a_week, 5, 2) * 7   - v_date_of_week + 1,
                   'yyyy-mm-dd')
      into v_first_date
      from dual;
end if;

return v_first_date;

END;

ITPub博客

查询某年的第多少周的周一的日期

最新文章