mysql - CakePHP LEFT JOIN 在有条件的多个表上

Question

我想使用这个 CakePHP 表单进行左连接。参见 CakePHP Book - section on Joining Tables

$options['joins'] = array(
    array('table' => 'channels',
        'alias' => 'Channel',
        'type' => 'LEFT',
        'conditions' => array(
            'Channel.id = Item.channel_id',
        )
    )
);
$Item->find('all', $options);

除了我的 LEFT JOIN 有一个带条件的从属表。在 MySQL 中，连接看起来像这样

LEFT JOIN (
    channels as Channel 
        INNER JOIN regions as Region ON ( Region.id = Channel.region_id and Region.id=1 )
) ON Channel.id = Item.channel_id

我可以使用 $options['joins'] 语法在 CakePHP 2.0 中做同样的事情吗？

Answer 1

所以经过一些摆弄之后，我发现这在 CakePHP 中起到了“诡计”。根据 SQL EXPLAIN，这比使用子查询在 LEFT 连接表上强制条件要快得多

$options['joins'] = array(
    array('table' => '(channels as `Channel` INNER JOIN regions as `Region`
                      ON ( `Region`.id = `Channel`.region_id and `Region`.id=1 ))',
//        'alias' => 'Channel',  // the alias is 'included' in the 'table' field
        'type' => 'LEFT',
        'conditions' => array(
            'Channel.id = Item.channel_id',
        )
    )
);
$Item->find('all', $options);