Question

I’ve got three tables

• posts
• tags
• posts_tags

I need to write some controller logic that selects and sets all posts that have the tag work

This means querying the tags to find the id for the queried tag, checking in the associated posts_tags table to find matches, using the post_id to return the correct posts from the posts table.

I’m not sure how to even begin this query, I’m new to CakePHP and could use a hand… Please?

If it helps, here’s my posts model relationship:

var $hasAndBelongsToMany = array(
        'Tag' => array(
            'className' => 'Tag',
            'joinTable' => 'posts_tags',
            'foreignKey' => 'posts_id',
            'associationForeignKey' => 'tag_id',
            'unique' => true,
            'conditions' => '',
            'fields' => '',
            'order' => '',
            'limit' => '',
            'offset' => '',
            'finderQuery' => '',
            'deleteQuery' => '',
            'insertQuery' => ''
        )
    );

My Tag table is made up of two fields: id and tag
My PostsTag table is made up of three fields: id, tag_id and post_id
My Posts table is made up of four fields: id, title, body and created

I found some code on the CakePHP Book that shows the below code:

$this->Recipe->Tag->find('all', array('conditions'=>array('Tag.name'=>'Dessert')));

They suggested that it was a similar idea, so I attempted to adapt:

$this->Post->Tag->find('all', array('conditions'=>array('Tag.tag'=>'work')));

However, this has not worked. This returns all Posts without filtering.

I took the advice of @Leo and tried to adapt his code to mine:

function getArticleByTagSql($tag) {
        $dbo = $this->getDataSource();
        $subQuery = $dbo->buildStatement(
                        array(
                    'fields' => array('DISTINCT(ArticlesTag.article_id)'),
                    'table' => "articles_tags",
                    'joins' => array(
                        array('table' => 'tags',
                            'alias' => 'Tag',
                            'type' => 'INNER',
                            'conditions' => array('ArticlesTag.tag_id = Tag.id')
                        )
                    ),
                    'alias' => "ArticlesTag",
                    'conditions' => array("Tag.tag" => $tag),
                    'order' => null,
                    'group' => "ArticlesTag.article_id",
                    'limit' => null
                        ), 
                $this
        );
        $subQuery = ' Article.id  IN (' . $subQuery . ')';
        return $dbo->expression($subQuery);
    }

Controller:

$this->set('articles', $this->paginate(array(
            'conditions' => $this->Article->getArticleByTagSql('work')
        )));

However, whatever I type in the paginate() method as a key – in this case ‘conditions’ appears in the query and I can’t figure out why – I keep getting unknown column ‘conditions’ errors. The error is with the paginate function, the data returns correctly without it, but I cannot use the paginator without it. It’s like a catch 22

Cheers,
Dan

Answer 1

Daniel this question is actually answered in the Cake documentation when describing the HABTM relationship betweens Receipe/Tag

I answered this question for someone who had a similar issue with an Article/Tag models, that answer used a subquery