mysql - CakePHP，不加入或排除加入？

Question

表格是:

units (id,...)   // approx' 10,000 units
contracts(id, unit_id, active, ...) // approx 50,000 records

我想获取所有没有附加契约(Contract)的单位(以及contracts.active=true)。

我的想法是: 使用NOT IN: 从单位中选择* 其中 id NOT IN(从contracts.active = true 的合约中选择unit_id) 或者:

select * from units u
left join contracts c
on c.unit_id = u.id
where c.unit_id is null

并且，如果有一种本地方法可以在蛋糕中做到这一点，请告诉我:)

谢谢

Answer 1

根据您的其他连接，NOT IN 可能会给您带来糟糕的性能。我建议使用以下 SQL 查询:

SELECT * FROM units AS u
LEFT JOIN contracts AS c
ON (c.unit_id = u.id AND c.active = 1)
WHERE c.id IS NULL

根据cakephp documentation :

Cake can also check for null fields. In this example, the query will return records where the post title is not null:

array ("NOT" => array (
        "Post.title" => null
    )
)

因此，根据您的模型的设置方式，这可能适合您:

$joins = array(('table' => 'contracts',
                'alias' => 'Contracts',
                'type' => 'LEFT',
                'conditions' => array('Contracts.active' => 0)));
$conditions = array('Contracts.id' => NULL);
$units = $this->Units->find('all', array('joins' => $joins, 'conditions' => $conditions));