搜索匹配另一张表时很慢

[fkueyga6]

。。。。省略
if($benxiao>0)
{
$sql_where.=" and huodong.mobile not in (SELECT mother_mobile FROM ".$fdyu->table('oa_xueyuan')." where school_id=".$school_id.") and huodong.mobile not in (SELECT father_mobile FROM ".$fdyu->table('oa_xueyuan')." where school_id=".$school_id.") and huodong.mobile not in (SELECT home_tel FROM ".$fdyu->table('oa_xueyuan')." where school_id=".$school_id.")";//这里如果oa_xueyuan这张表里的数据多的话，搜索起来就很慢，有什么其它的方法可以快一点吗？
}

$sql = "SELECT huodong.* FROM
".$fdyu->table('oa_huodong_baoming')." as huodong
".$sql_title." ".$sql_benxiao." ".$sql_where." order by feiyong desc,huodong_baoming_id desc";