How i can compare the result in one query or two? - php

Question

I am trying to fetch last 10 topics from smf database but topics are in two separate tables.
Subject, Post Time and Message ID in smf_messages.
Topic ID and Topic First Message in smf_topics.
I wrote this code to fetch topics but i dont know how to compare these two results.
$result = mysql_query("select subject,id_msg,id_topic from smf_messages");
$result2= mysql_query("select id_first_msg from smf_topics");
if(mysql_num_rows($result)!=0)
{
while($read = mysql_fetch_object($result))
{
if ($read->id_msg==$read->id_topic) {
echo "<a href='../index.php?topic=" . $read->id_topic . "'>".$read->subject."</a><br>";
}
}

Answer 1

You probably want the following query
select subject, id_msg, id_topic, id_first_msg
from smf_messages
left join smf_topics on smf_message.id_msg = smf_topics.id_first_msg

Answer 2

bind the records by joining in sql:
select subject id_msg, id_topic, id_first_msg from smf_messages
join smf_topics on smf_messages.id_msg = smf_topics.id_topic

Answer 3

mysql have many many options, with a small google search you could found about left join.
tuttorial and examples.
Fist thing you have to do is stop using mysql_* and start using mysqli_* or pdo learn about sql injections
Your query should look like this.
select smf_messages.subject,smf_messages.id_msg,smf_messages.id_topic from smf_messages left join smf_topics on smf_topics.id_first_msg=smf_messages.id_msg

Answer 4

If you want to do that without using SQL, this is my solution it's not good but you can have an idea of how it works:
$messages = array();
$topics = array();
while($readmessage = mysql_fetch_object($resultmessage)) {
array_push($messages, $readmessage);
}
while($readtopic = mysql_fetch_object($resulttopic)) {
array_push($topics, $readtopic);
}
foreach ($topics as $topic) {
$result = array_search($topic->id_first_message);
if($result != true){
//HERE $result IS THE INDEX OF FIRST MESSAGE IF IT IS IN THE MESSAGES ARRAY
$messages[$result].id_msg //Access message attributes
}
}