PHP Activerecord Model Count Associations

问题

I have three tables:

Member

MemberBranch

Branch

The Member can have many Branches through MemberBranch. And a Branch can have many Members etc.

What I want to be able to do is get a count of how many members a branch has.

$branch = Branch::find_by_title('London');
$branch->number_of_members; // Will equal how many members have the branch through MemberBranch

How would I go about doing this?

回答1:

Try this:

SELECT B.*, (SELECT count(*) as total from MembersBranch where branch_id = B.id) as total FROM Branch AS B;

回答2:

Just incase anyone else has a similar problem, I have found a solution (albeit a little hacky)

class Branch extends \ActiveRecord\Model {

    static $has_one = array(
        array(
            'members',
            'class_name' => 'MemberBranch',
            'primary_key' => 'id',
            'foreign_key' => 'branch_id',
            'select' => 'COUNT(`membership_id`) AS `total`'
        )
    );
}

This creates a new association but does the SQL query we want using the select property. The number of members per branch can now be accessed like:

$branch->members->total

The reason I used $has_one as opposed to $has_many is that $has_many will always return an array of objects even if there is only one object. so using $has_many would have meant accessing the total like so:

$branch->members[0]->total

Save your keystrokes :)

来源：https://stackoverflow.com/questions/21290934/php-activerecord-model-count-associations

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