我)这两者之间哪一个更有效: Select A.* from A, B where A.b_id = B.id
或 Select A.* from A where A.b_id in (select id from B);
二)如何Select A.* from A where A.b_id in (select id from B);真的有用吗?它是否在内部翻译成类似Select A.*
我的代码: $fileid = $_GET['imgid'];
$fileid = (int)$fileid; //id is int type in photos table
require 'database.php';
//get the image sourc name
$q = "SELECT src form photos WHERE id='$fileid'";
$r