php - 多查询和结果连接

Question

require_once("./Connections/root.php");
session_start();
$user = $_SESSION['MM_Username'];
$q = mysql_query("SELECT id FROM performer WHERE username = '$user'");
$r = mysql_fetch_assoc($q);
$q1 = mysql_query("SELECT poster_id, wall_msg FROM performer_info WHERE id = '$r[id]'");
$r1 = mysql_fetch_assoc($q1);
$q2 = mysql_query("SELECT username FROM performer WHERE id = '$r1[poster_id]'");
$r2 = mysql_fetch_assoc($q2);

echo $r2['username'] . " : " . $r1['wall_msg'];

是否可以在单个查询和结果中使用所有这些查询？

我想，我需要使用内部连接，但我不知道该怎么做

$_SESSION['MM_Username'] 是登录用户，用户名

Answer 1

您可以使用类似的查询

select wall_msg from performer_info where poster_id = (select id from performer where username = '$user')

您已经知道的用户名...和 ​​wall_msg 可以从这个查询的结果中获得。

编辑：

 select p.username, t.wall_msg from performer p, (select poster_id, wall_msg from performer_info where id=(select id from performer where username= '$user'))t where p.id = t.posterid;

这仅在内部查询返回单个结果时才有效。希望能帮助到你。

Answer 2

内部连接怎么样？

SELECT t.username , pi.wall_msg 

FROM performer t

INNER JOIN performer_info pi ON pi.id = t.id

WHERE t.username LIKE '%$user%'