Question

my foundation on SQL is pretty weak so I hope you could bear with me. I have three tables: contents, categories, and categorization. The setup was chosen since some content will belong to one or more categories.

I want to fetch contents and its corresponding categories.

This is an overly-simplified version of the current script, without error-checking routines:

$q = "SELECT * FROM contents WHERE contents.foo = 'bar'"
$resource = mysql_query($q);
$categoryFilter = array();

$q2 = "SELECT * FROM categorization WHERE ";
while($content = mysql_fetch_assoc($resource))
{
    $categoryFilter[] = "content_id='" . $content["id"] . "'";
}

if(count($categoryFilter))
{
    $q2 .= implode(" OR ", $categoryFilter);
    mysql_query($q2);
}

That’s the gist of it. I hope you get what I am trying to do. I don’t know if I can actually use JOINS the content_id may be present in multiple rows in categorization. So what I did was to simply append multiple OR‘s, trying to fetch items one by one. I really would not like to use multiple queries in this scenario. I hope anyone could suggest an approach

Thanks for your time

Answer 1

One query should be enough to fetch data from all three tables:

SELECT categories.category_id #, other fields
FROM contents
INNER JOIN categorization ON contents.content_id = categorization.content_id
INNER JOIN categories ON categorization.category_id = categories.category_id
WHERE contents.content_id = 1 # AND other filters

Tweak the columns in the SELECT clause and/or conditions in WHERE clause according to your needs.