Question

I have an activity table with 3 $belongsTo reference keys. I need the join information from these id’s i.e. to show the commenttext – I don’t want to store the text twice… (same for post and topic).

Activity table: id | post_id | comment_id | topic_id
In each row only post_id OR comment_id OR topic_id is set, the other two id fields are NULL.

So i.e. if post_id = 55, comment_id = NULL, topic_id = NULL I get this:

Array
(
[0] => Array
    (
        [Activity] => Array
            (
                [id] => 1
                [post_id] => 55
                [comment_id] => 
                [topic_id] => 
            )

        [Post] => Array
            (
                [id] => 55
                [name] => Post #1
                [description] => This is Post #1.
                ...
            )

        [Comment] => Array
            (
                [id] => 
                [post_id] => 
                [titel] => 
                [description] => 
                ...
                [created] => 
                [modified] => 
            )

        [Topic] => Array
            (
                [id] => 
                ...
                [created] => 
                [modified] => 
            )
    )

[1] => Array
    (
        ...

Is there a way to join only if the reference id is NOT NULL? I don’t want to kill the empty arrays after the find with a php for-each loop.

Another idea was this database table: id | activitytype_id | refid to join with dynamic binding the necessary table depending on the activitytype_id. – That didn’t work as well…

That’s what I want – is that possible?

Array
(
[0] => Array
    (
        [Activity] => Array
            (
                [id] => 1
                [post_id] => 55
                [comment_id] => 
                [topic_id] => 
            )

        [Post] => Array
            (
                [id] => 55
                [name] => Post #1
                [description] => This is Post #1.
                ...
            )
    )

[1] => Array
    (
        [Activity] => Array
            (
                [id] => 2
                [post_id] => 
                [comment_id] => 2
                [topic_id] => 
            )

        [Comment] => Array
            (
                [id] => 2
                [post_id] => 4
                [titel] => Blabla
                [description] => This is the comment description
                ...
                [created] => 2011-01-01 01:30:00
                [modified] => 2011-01-01 01:30:00
            )
    )

[2] => Array
    (
        ...

Thanks in advance! 🙂

Answer 1

You would need to query the database to find out which IDs are null and then query the database a second time to grab the related data.

$activity = $this->Activity->read(null, 1);
// some logic to find foreign key with non-null value
$activity[$model] = $this->{$model}->read(null, $id);

I wouldn’t waste your time writing two queries; let CakePHP get all the results in a single query. 🙂

$activity = $this->Activity->findById(1);

Just add this to your model to filter out empty values from results:

public function afterFind($results, $primary = false) {
    return Hash::filter($results);
}