How can I make this simple block shorter and better? - php

Question

I'm using the following not well thought code block to retrieve categories and it's topics.
$query1 = "SELECT * from categories";
$result = mysql_query($query1);
while ($out = mysql_fetch_assoc($result)){
//category
print '<h2>' . $out['name'] . '</h2>';
$query2 = "SELECT * from topics where fkid = $out[id]";
$result2 = mysql_query($query2);
while($top = mysql_fetch_assoc($result2)){
//topic
print $top['name'] . '<br>';
}
}
The above does the trick. I know this is not the most practical and this being the reason I ask the group.
How can I better this so it's more practical and simple?

Answer 1

A classical case for a JOIN:
SELECT * FROM categories JOIN topics ON categories.id = topic.fkid ORDER BY categories.name;
Then to print, we only print the header if it has changed (thanks, Rajasur!):
$catname = "";
while ($out = mysql_fetch_assoc($result))
{
if ($out["name"] != $catname) // maybe need strcmp here
{
$catname = $out["name"];
print($catname)
}
/* print the rest */
}

Answer 2

Just use a single query that joins the two tables.
$query = "SELECT categories.name AS category_name, topics.name AS topic_name
FROM categories JOIN topics ON categories.id = topics.fkid
ORDER BY categories.name ASC, topics.name ASC";
$resultSet = mysql_query($query);
$currentCategory = "";
while ($cRecord = mysql_fetch_assoc($resultSet)) {
if ($currentCategory != $cRecord['category_name']) {
$currentCategory = $cRecord['category_name'];
echo "<h2>" . $currentCategory . "</h2>";
}
echo $cRecord['topic_name'] . "<br/>";
}
mysql_close($resultSet);