oracle SQL问题请教

[sui366]

在oracle中

从当前日期算起得到指定天数（不如5天或三天）前的日期。

这条语句该如何写?

请各位大侠多多指教...

[真的不知道取什么名]

select sysdate-5 from dual

[sui366]

不好意思 问题补充下：指定的天数是工作日，需要过滤双休日（其他节假日不考虑）

[xman_78tom]

-- 星期天作为一个星期的第一天
declare
 days number:='&days';
 inc number;
begin
 select count(1) into inc
 from dual
 where to_char(sysdate+level,'D') in (1,6)
 connect by level<=days;
 dbms_output.put_line(sysdate+days+inc);
end;
/

[xman_78tom]

-- 除去双休日后，第 days 天的日期
declare
 days number:='&days';
 dates date:=sysdate;
 inc number;
begin
 loop
  select count(1) into inc from dual
  where to_char(dates+level,'D') in (1,6)
  connect by level<=days;
  exit when inc=0;
  dates:=dates+days; days:=inc;
 end loop;
 dbms_output.put_line(dates+days);
end;
/

[xman_78tom]

declare
 days number:='&days';
 dates date:=sysdate;
 inc number;
begin
 loop
  select count(1) into inc from dual
  where to_char(dates+level,'D') in (1,7)
  connect by level<=days;
  exit when inc=0;
  dates:=dates+days; days:=inc;
 end loop;
 dbms_output.put_line(days);
 dbms_output.put_line(dates+days);
end;
/