没有主键的表上的CodeIgniter查询

Question

For some customers I am working on a project which is using a MySQL database.

I need to implement a search functionality which should be able to search in the database the devices with all the features selected. I am using CodeIgniter. The problem is the structure of the table.

I've found out that the table contains 2 columns: ID_D (the id of the device) and ID_F (the id of the feature). Basically the table doesn't contain any primary key (that's why I cannot execute any join at all).

So, it's also possible that a device id can appear in 10 rows for each feature it has. When I execute the search, I have a list of the features ID and I should be able to read only the devices with all the features selected.

if (isset($feature_array)) {
    foreach($feature_array as $key => $row) {
        $this->db->where('f_id',$row['f_id']); 
    }
}

Naturally, something like that won't work. Any ideas?

Answer 1

I think this might solve your problem, in case the feature ids are unique and do not contain spaces. In case they do contain spaces you should select a separator, that is not in the range of the feature ids.

Basically the code uses the mySQL group_concat function to concatenate all feature ids and matches the created string by all searched features. This finds all devices, that support at least the given set of features.

CI itself does not support that fucntion, so it is added by a workarround in the select method.

Also this might be a bit load intensive if it is called on a large table. Maybe someone else got a faster solution?

$this->db->select(['ID_D', 'GROUP_CONCAT(ID_F SEPARATOR \' \']) as id_f_concatenated']);
foreach($feature_array as $row) {
    $this->db->where("id_f_concatenated REGEXP '{$row['id_f']} | {$row['id_f']}|^{$row['id_f']}$'");
}
$this->db->group_by('ID_D');
$result = $this->db-get('tablename');

EDIT: Changed the LIKE to an REGEXP to make sure, that the feature id 112 is not matched by the id 12, without making the expression to complicated.