PHP Codeigniter - Join a table if column does not equal NULL

Question

Setup:

Codeigniter 3 running on a variant of PHP 5 server. Using the Query Builder to deal with the db.

Background:

Creating a software that has a client profile. Users can add multiple notes to the profile, and link a contact to that note. The profile then displays all the notes and the contact on the corresponding profile, using the join() method from Codeigniter 3's Query Builder.

Issue:

A note can be added without a client contact, in the case of a generalised note. This sets the default value of NULL in the DB which in turn prevents the client_model from returning the notes, because it cant join the tables.

Current code:

function get_client_notes($client_id)
{   
    $this->db->join('nh_note_types', 'nh_note_types.type_id = nh_client_notes.client_notes_type');
    $this->db->join('nh_user_profiles', 'nh_user_profiles.user_profile_user_id = nh_client_notes.client_notes_added_by');
    $this->db->join('nh_client_contacts', 'nh_client_contacts.client_contact_id = nh_client_notes.client_notes_client_contact_id');
    $this->db->order_by("client_notes_added_date", "desc");
    $query = $this->db->get_where('nh_client_notes', array('client_notes_client_id' => $client_id));
    return $query;
}

Currently if the value for client_notes_client_contact_id is NULL it will not return any data for that row.

What I am trying to find out is if there is a way to do the following: IF the client_notes_client_contact_id is not null then join the tables, else carry on past.

Or any other way that would join the tables if there is a value and where it is NULL , then don't join.

Any help is appreciated!

Answer 1

Your current MySQL query with the above Query builder would 'build' like this:

SELECT 
   * 
FROM 
   nh_client_notes
JOIN nh_note_types ON 
   ( nh_note_types.type_id = nh_client_notes.client_notes_type )
JOIN nh_user_profiles ON 
   ( nh_user_profiles.user_profile_user_id = nh_client_notes.client_notes_added_by )
JOIN nh_client_contacts ON 
   ( nh_client_contacts.client_contact_id 
       = 
     nh_client_notes.client_notes_client_contact_id 
   )
WHERE 
   client_notes_client_id = 479
ORDER BY  
   client_notes_added_date DESC

However, this will require all the JOINs to have an matching ID Available. Thus the correct MySQL would be LEFT JOIN on client_notes_client_contact_id key, which is as you've requested to be conditional .

In this instance, adjust your Query builder to have a third parameter on the join() to make this 'left'.

<?php
$this->db->join(
  'nh_client_contacts', 
  'nh_client_contacts.client_contact_id = nh_client_notes.client_notes_client_contact_id', 
  'left' 
);
?>

In doing so, this'll correct your query to bring back client_notes regardless of client_notes_client_contact_id .