oracle

[yl9]

请问oracle中有没有取随机数的函数，如SQLSERVER中的RAND（），
ORACLE中的时间能不能取到毫秒

[dragoncool]

Limu
to_char(sysdate,'MMDDHHMISS')只能到秒，不知道什么函数可以精确到毫秒
谢谢

[dragoncool]

use sequence
建立一个 sequence 做一个函数，得到唯一的数值即可。

[Limu]

应该有，仔细找找，最好到Books Online里去找，Oracle的时间可以精确到毫秒.

[9Thoughts]

很遗憾！这两个问题的答案全是否定的。

[lynx]

随机数发生器:
CREATE OR REPLACE package pk_rand
is
/*****************************************************************
* Written by Malcolm Turner Dec 1999
* based on a earlier Forms3 procedure
* This package returns a random number between 0 and 1
* Optionally, the range returned may be set with
* set_range(lower,upper)
* in which case the number returned will be an integer.
* This may be over-ridden with the optional switch in this procedure
* For repeatability in testing, the initial "seed" value used
* may be set by the user using procedure set_seed
* *
* *
* This package is offered freely to the Oracle community in the
* hope that it will be useful.
* *
* Please send any comments/suggestions to
*
* [e-mail]
*
*
******************************************************************/
procedure set_range(p_lower in number,p_upper in number,p_integer in varchar2 := 'Y');
procedure set_seed(p_seed in number);
procedure rand(p_result out number) ;
function f_rand return number;
pragma restrict_references(f_rand,WNDS);
end;
/

CREATE OR REPLACE package body pk_rand
is
v_range_lower number := 0;
v_range_upper number := 1;
v_lastval number;
v_rand number;
v_result number;
v_integer boolean := FALSE;
cursor c_seed is
select to_char(sysdate,'SSSSSDDDHHSSSSS')
from dual;

procedure set_seed(p_seed in number)
is
begin
v_lastval := p_seed;
end;

procedure set_range(p_lower in number,p_upper in number
,p_integer in varchar2 := 'Y')
is
begin
v_range_lower := p_lower;
v_range_upper := p_upper;
if p_integer = 'Y' then
v_integer := TRUE;
else
v_integer := FALSE;
end if;
end;

procedure rand(p_result out number)
is
begin
p_result := f_rand;
end;

function f_rand return number is
/* Fixed values used in generation */
a number := 25214903917;
c number := 11;
m number := power(2,48);
begin
/* Compute next random number */
v_rand := ((a * v_lastval + c ) mod m );
/* Store it as seed value in next calculation */
v_lastval := v_rand;
/* Get output between 0 and 1 */
v_rand := v_rand / m;
/* Multiply up to required range */
if v_integer then
/* Increment the range by 1 to allow for truncation */
v_result := v_rand * ((v_range_upper +1) - v_range_lower ) +
v_range_lower;
v_result := trunc(v_result);
else
/* Just multiply to expand the answer */
v_result := v_rand * (v_range_upper - v_range_lower ) + v_range_lower;
end if;
return v_result;
end;

/* And now the initialisation code */
begin
open c_seed;
fetch c_seed
into v_lastval;
close c_seed;
end;
/
借花献佛,希望有用!:)