我在一个名为connect.php的文件中使用它：
$username_mysql = "root";
$password_mysql = "";
$database_mysql = "bdd_imvert";
//$database_mysql = "imprimvert_renouvellement";
$db = @mysql_connect($hostname_mysql, $username_mysql, $password_mysql) or die(mysql_error());
mysql_select_db($database_mysql,$db);
$hostnameivert_mysql = "localhost";
$usernameivert_mysql = "root";
$passwordivert_mysql = "";
$databaseivert_mysql = "ivert";
//$database_mysql = "imprimvert_renouvellement";
$db1 = @mysql_connect($hostnameivert_mysql, $usernameivert_mysql, $passwordivert_mysql) or die(mysql_error());
mysql_select_db($databaseivert_mysql,$db1);`
我将其包含在包含以下内容的页面中：
$sql = "select * from ivert_users where id=".GetSQLValueString($user_id,"int");
$re = @mysql_query($sql,$db)
但是，当我这样做时，我收到一个错误：
"ivert.ivert_users"不存在
我不确定为什么我会收到此错误，任何帮助将不胜感激。
你的代码没有问题。我尝试了同样的方法，它对我有用。您的查询一定有问题。因为错误消息显示连接已发生，但查询返回了错误。参考这个 它可能会有所帮助。
或者第二个原因可能是您没有为第一个数据库定义主机。
<?php
$hostnameivert_mysql = "localhost";
$username_mysql = "root";
$password_mysql = "pma";
$database_mysql = "olivenation";
$db = @mysql_connect($hostname_mysql, $username_mysql, $password_mysql) or die(mysql_error());
mysql_select_db($database_mysql,$db);
echo ("<pre>");print_r($db);echo("</pre>");
$hostnameivert_mysql = "localhost";
$usernameivert_mysql = "root";
$passwordivert_mysql = "pma";
$databaseivert_mysql = "practical";
$db1=@mysql_connect($hostnameivert_mysql, $usernameivert_mysql, $passwordivert_mysql) or die(mysql_error());
mysql_select_db($databaseivert_mysql,$db1);
echo ("<pre>");print_r($db1);echo("</pre>");
$sql = "select * from product_master where id=1";
$re = @mysql_query($sql,$db);
echo ("<pre>");print_r(mysql_fetch_array($re));echo("</pre>");
$sql = "select * from users";
$re = @mysql_query($sql,$db1);
echo ("<pre>");print_r(mysql_fetch_array($re));echo("</pre>");
?>