[英]How to perform MySQLi query based off of another query result set?
我知道有一種方法可以使用JOIN
組合這三個查詢,但是我無法解決這個問題。
我正在做的是首先檢索MessageID
和SubscriberID
。 根據這些結果,我收集消息的數據和訂戶的數據:
$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 $to exists
// Send email & do other stuff
}
}
}
}
基本上,我試圖在一個查詢中盡可能獲取Subject
, Body
, Email
, FirstName
, LastName
和History
。
我知道必須有一種更有效的方法。
因此,此查詢應該在代碼的if($to)
段中為您提供一些建議。 您應該在該行中擁有所有可用的東西。
$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'];
}
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