不能猜测,应该验证一下set_time_limit(0); mysql_connect(); mysql_select_db('test'); mysql_query('create temporary table a (ch varchar(9))');$len = 1000000; for($i=0; $i<$len; $i++) { $c = random_str(9); mysql_query("insert into a values ('$c')") or die(mysql_error()); } $rs = mysql_query('select ch, count(*) as cnt from a group by 1 having cnt>1') or die(mysql_error()); while($r = mysql_fetch_assoc($rs)) { echo join(':', $r), PHP_EOL; } 一次产生一百万个确实没有重复
那就是
pow(36, 4) = 1679616
也还是能够满足的
这样写产生9位的随机字符串 100w 应该没问题吧
/*
* 随机字符串
*/
function random_str($length)
{
$arr = array_merge(range('a', 'z'),range(0, 9));
$str = '';
$arr_len = count($arr);
for ($i = 0; $i < $length; $i++)
{
$rand = mt_rand(0, $arr_len-1);
$str.=$arr[$rand];
}
return $str;
}
mysql_connect();
mysql_select_db('test');
mysql_query('create temporary table a (ch varchar(9))');$len = 1000000;
for($i=0; $i<$len; $i++) {
$c = random_str(9);
mysql_query("insert into a values ('$c')") or die(mysql_error());
}
$rs = mysql_query('select ch, count(*) as cnt from a group by 1 having cnt>1') or die(mysql_error());
while($r = mysql_fetch_assoc($rs)) {
echo join(':', $r), PHP_EOL;
}
一次产生一百万个确实没有重复