PHP/mySQL - how to fetch nested rows into multidimensinal array

Question

Coming from another question of mine where I learnt not to EVER use db queries within loops I consequently have to learn how to fetch all the data in a convenient way before

Answer 1

The query should look something like this:

SELECT * FROM scales
INNER JOIN items ON scales.id = items.scale_id

If you want to iterate through with nested loops, you'll need to pull this data into an array - hopefully you're not pulling back so much that it'll eat up too much memory.

$scales = array();

while ($row = mysql_fetch_assoc($data))
{
    if (!isset($scales[$row['scale_id']]))
    {
        $row['items'] = array();
        $scales[$row['scale_id']] = $row;
    }

    $scales[$row['scale_id']]['items'][] = $row;
}

Then you can loop through:

foreach ($scales as $scale)
{
    foreach ($scale['items'] as $item)
        ; //... do stuff
}

Note: this is somewhat naive in that $scale and $item will both contain fields from BOTH tables... if that's a problem then you need to change the assignments in the loop above to pull out only the fields you want.