Question

例如，我有两个查询：

return $this->model->where('closed_at', null)
            ->whereHas('users', function ($query) {
                $query->where('id', '=', auth()->user()->id);
            })         
            ->with(['product:id,title', 'in_works' => function ($query) {
                $query->where('user_id', '=', auth()->user()->id);
            }])
           ->get();

它工作正常，并通过join（急切加载）返回1个查询：

select * from `order` where `closed_at` is null and exists (select * from `user` inner join `user_order` on `user`.`id` = `user_order`.`user_id` where `order`.`id` = `user_order`.`order_id` and `id` = ?)

但类似查询

return $this->model->where('closed_at', null)
            ->with(['product:id,title', 'in_works' => function ($query) {
                $query->where('closed_at', '=', null);
            }])->get();

返回3个查询，为什么？

select * from `order` where `closed_at` is null
select `id`, `title` from `product` where `product`.`id` in (1, 2)
select * from `in_work` where `in_work`.`order_id` in (1, 2) and `closed_at` is null

Answer 1

通过急切加载（即使用with）添加到模型的每个关系都通过附加查询来查询。

这是您拥有的：

模型查询

select * from `order` where `closed_at` is null -- Model

使用product:id,title查询

select `id`, `title` from `product` where `product`.`id` in (1, 2)

使用in_works查询

select * from `in_work` where `in_work`.`order_id` in (1, 2) and `closed_at` is null

请注意，在情况（2）和（3）中，(1,2)对应于从第一个查询获得的order的标识符。

whereHas将进一步优化原始模型查询，因此会影响返回的总结果。对于您而言，以下是whereHas('users',...)查询的结果：

select * from `order` where `closed_at` is null and exists (select * from `user` inner join `user_order` on `user`.`id` = `user_order`.`user_id` where `order`.`id` = `user_order`.`order_id` and `id` = ?)

当模型查询实际上未产生任何结果时，则实际上不执行任何关系查询。

为什么在急切加载中雄辩地分隔查询？

1 个答案: