php mysql : How to list two tables with related data? - php

Question

I had a simple tree structure output question,
In the beginning I use two mysql_query, one is to get the pro_class data, include pro_class.cid , and to query next table by cid, like:
mysql_query("select * from pro_class ");
mysql_query("select * from pro where cid='pro_class.cid' ");
but I want to using one query,how can I accomplish?
table: pro_class
cid 　title 　time
1　　PEOPLE　 2013/8/31
4　　CAR　　　2013/8/30
7　　Music　 2014/7/10
table: pro
id 　cid 　title 　content 　time
1　 1　　Mark xxxx 2010/8/31
2　 4　　BMW xxxx 2012/2/12
3　 1　　Joe xxxx 2015/1/31
4　 7　　sweet xxxx 2013/8/22
5　 1　　KEN xxxx 2010/1/31
The structure should be
PEOPLE
-Mark
-Joe
-KEN
CAR
-BMW
Music
-sweet
I want to the Html output can like this (by php+mysql)
<ul>
<li class="">PEOPLE</li>
<ul class="sub">
<li><a title='Mark' href='?id=1'>Mark</a></li>
<li><a title='Joe' href='?id=3'>Joe</a></li>
<li><a title='KEN' href='?id=5'>KEN</a></li>
</ul>
<li class="">CAR</li>
<ul class="sub">
<li><a title='BMW' href='?id=2'>BMW</a></li>
</ul>
<li class="">Music</li>
<ul class="sub">
<li><a title='sweet' href='?id=4'>sweet</a></li>
</ul>
</ul>
How do I to coding sql?
$rst = mysql_query("select ?????? ");
while($row = mysql_fetch_object($rst)){
echo <<<EOD
<ul>
<li class="">{$row->pro_class.title}</li>
<ul class="sub">
<li><a title='{$row->pro.title}' href='?id={$row->pro.id}'>{$row->pro.title}</a></li>
</ul>
</ul>
EOD;
}

Answer 1

You can try this approach. It uses group_concat.
<?php
$query = "select pc.title as title, group_concat(p.title) as inner_titles FROM pro_class pc LEFT JOIN pro p ON p.cid=pc.cid GROUP BY p.cid ORDER BY p.title";
$result=mysqli_query($query);
print "<ul>";
while($res=mysqli_fetch_array($result)) {
print "<li>" . $res['title'] . "</li>";
$arr = explode(",",$res['inner_titles']);
if(count($arr)>0) {
print "<ul>";
foreach($arr as $val) {
print "<li>" . $val . "</li>";
}
print "</ul>";
}
}
print "</ul>";
?>

Answer 2

You can use a mysql function called group_concat which will merge a number of rows into a string that is delimited by something you choose.
The following will get you most of the way to getting what you want - you can probably work out the display part on your own though.
select
pro_class.title,
GROUP_CONCAT(pro.title SEPARATOR ',') AS listItems
from
pro_class
left outer join pro
on pro_class.cid=pro.cid
group by
pro_class.title