我知道有一种方法可以使用JOIN组合这三个查询，但我就是无法理解它。
我要做的是首先检索MessageID和SubscriberID。根据这些结果，我收集消息的数据和订阅者的数据:
$queued = $db->select("SELECT MessageID, SubscriberID FROM mailing_queue WHERE Paused = 0 ORDER BY StartDate ASC LIMIT 500");
if (!empty($queued)) { // if $queued exists
$i = 0;
foreach ($queued as $key => $value) {
$msg = $db->selectRow("SELECT Subject, Body FROM mailing_messages WHERE ID = '$value[MessageID]' LIMIT 1"); // Returns single row
if ($msg) { // If $msg exists
$to = $db->selectRow("SELECT Email, FirstName, LastName, History FROM mailing_subscribers WHERE ID = '$value[SubscriberID]' LIMIT 1"); // Returns single row
if ($to) { // If $to exists
// Send email & do other stuff
}
}
}
}
基本上，如果可能的话，我试图在一个查询中获得Subject, Body, Email, FirstName, LastName和History。
我知道一定有更有效的方法来做这件事。
所以这个查询应该给你一些东西来检查你的代码的if($to)段。你应该有行中所有可用的东西。
$queued = $db->select(
"SELECT
mailing_queue.MessageID,
mailing_queue.SubscriberID,
mailing_messages.Subject,
mailing_messages.Body,
mailing_subscribers.Email,
mailing_subscribers.FirstName,
mailing_subscribers.LastName,
mailing_subscribers.History
FROM mailing_queue
INNER JOIN mailing_messages ON mailing_messages.ID = mailing_queue.MessageID
INNER JOIN mailing_subscribers ON mailing_subscribers.ID = mailing_queue.SubscriberID
WHERE mailing_queue.Paused = 0
ORDER BY mailing_queue.StartDate
ASC LIMIT 500");
foreach($queued as $key=>$to){
//whatever your send your email code is, demonstration:
echo $to['Subject'];
echo $to['SubscriberID'];
echo $to['FirstName'];
}