php语句，怎么从数据库中随机获取数据字段。

if(!$con = mysql_connect("localhost","root","root")){die(mysql_error())}

mysql_select_db("ali_xt")

mysql_query('set names utf8')

//找出ali_admin表的字段

$res = mysql_query('show columns from ali_admin')

//将数据给弄出来

$data = array()

while ($row = mysql_fetch_assoc($res, MYSQL_NUM)) {

$data[] = $row

}

//随机个数，默认5

$rand_times = 5

$rand_times = count($data)<$rand_times?count($data):$rand_times

$result = array()

for( $i=0$i<$rand_times$i++ ){

$result[] = $data[rand(0,count($data)-1)][0]

}

echo "<pre>"

print_r($result) //输出5个随机字段

mysql_close($con)

//纯手写的，不明白可以问我，记得给分

* MySQL 随机取记录

*

* @param $t 表

* @param $c ID列，默认为id

* @param $n 取多少个

* @param $w 条件语句

* @param $f bool 是否强制以多维数组形式返回，默认false

* @return array 取1个直接返回结果数组(除非$f为true)，取>1个返回多维数组，用foreach取出

*/

function rand_row($t , $c = 'id' , $n = '1', $w = '' , $f = false) {

$m=new mysqli(mysqli信息，自行查找php文档)

if (!empty($w)) {

$w = ' AND '.$w

}

$sql = "SELECT * FROM `{$t}` WHERE {$c} >= (SELECT floor(RAND() * (SELECT MAX({$c}) FROM `{$t}`))) {$w} ORDER BY {$c} LIMIT {$n}"

$xq = $m->query($sql)

$r = array()

while ($x = $m->fetch_array($xq)) {

$r[] = $x

}

if ($f == false &&count($r) == 1) {

return $r[0]

} else {

return $r

}

}