So, one problem that we’ve come across is a way to relate several tables (or weblogs as EE calls them) together. An example would be like so: doctors, their specialties, and the locations of their practice. A likely scenario is a user wants to find out what locations provide a certain specialty. Thus, you have to use the doctors as the bridge of the data.

In Expression Engine you can use a related field to tie two tables of data together. For instance, I can tie a Doctor to a certain specialty using a related field. But, creating a bridge between the doctors’ specialties and all the locations is not possible without a little custom programming.

Also, throw in the mix that doctors can have offices at several locations, and you’ve got a hairy set of data. (We’re using the multi-relationship plug-in from here).

So, let’s get to the code.

<?php
global $DB;
$addresses = $DB->query("SELECT * FROM `exp_weblog_data` WHERE weblog_id = 6");
foreach($addresses->result as $address){
	$doctors = $DB->query("SELECT * FROM `exp_weblog_data` WHERE weblog_id = 3");
	foreach($doctors->result as $doc){
		$rel_field_ids = array(2);
		$rel_field_ids_new = '';
		$rel_field_ids[0] = $doc['field_id_34'];
		$rel_field_ids[1] = ereg_replace("\r",",",$doc['field_id_35']);
		$rel_field_ids_new = "'" . implode("','",$rel_field_ids) . "'";
		$specialties = $DB->query("SELECT * FROM exp_relationships WHERE rel_id IN (" . $rel_field_ids_new . ")");
		foreach($specialties->result as $specialty){
			if($specialty['rel_child_id'] == $address['entry_id']){
				$specs[] = $specialty['rel_parent_id'];
			}
		}
	}

	if(sizeof($specs) > 0) {
		$specialties_ids = $DB->query("SELECT field_id_13 FROM exp_weblog_data WHERE entry_id IN(" . implode($specs,',') . ")");
		foreach($specialties_ids->result as $s_id){
			$related_spec = $DB->query("SELECT * FROM exp_relationships WHERE rel_id = " . $s_id['field_id_13']);
			$related_spec_title = $DB->query("SELECT title FROM exp_weblog_titles WHERE entry_id = " . $related_spec->row['rel_child_id']);
			if(!in_array($related_spec_title->row['title'],$titles_array)){ $titles_array[] = $related_spec_title->row['title']; }
		}
	}
	implode($titles_array,"','")
}
?>

So, in a nutshell the code above will compare the locations with the specialties using the exp_relationships table and the doctor as the bridge.

I had to think about it a bit, but you kinda get the idea. I hope this helps someone out there struggling with the same issue.

Happy coding.

Note: When copying this code make sure you replace the curly quotes.