php - MySQL查询: get the last row of related table on multi table selection

Question

我有 2 个这样结构的表

产品

• ID
• 标题

计划

• ID
• 产品 ID
• 价格
• 类型

基本上，这个想法是为每个产品设置多个价格，每个产品的最后一个计划将是其当前价格，如果其被删除或过期，它将回退到之前的计划

因此，如果产品有 2 个 ID 为 (1, 2) 的计划，则 id = 2 的计划将是其当前价格

我想展示他们最近计划的产品type = off

这是由 Laravel ORM Eloquent 生成的 SQL 查询

select * from `products` where exists
        (select * from `plans` where `products`.`id` = `plans`.`product_id`
                and `type` = 'off' 
                and `plans`.`deleted_at` is null) 
        and `products`.`deleted_at` is null

问题是它不会检查最后/当前计划，它会在所有计划中搜索...所以即使 id = 2 类型的计划未关闭并且如果 plan.id = 1 类型已关闭 我仍然会在查询中包含此产品
这是 PHP 代码:

$wonder_product = Product::whereHas('CurrentPlan', function ($q) {
    $q->where('type', 'off');
})->get();

Answer 1

尝试使用 GROUP BY 子查询:

$wonder_product = Product::whereHas('CurrentPlan', function ($q) {
    $q->where('type', 'off')
    ->whereIn('id', function ($subquery) {
        $subquery
        ->from(with(new CurrentPlan)->getTable())
        ->select(DB:raw('MAX(id)'))
        ->groupBy('product_id');
    });
})->get();

或者，如果您可以接受原始子查询:

$wonder_product = Product::whereHas('CurrentPlan', function ($q) {
    $q->where('type', 'off')
      ->whereRaw('id in (select max(id) from plans group by product_id)')
})->get();

如果我没记错的话，这两种方法都应该生成如下查询:

select * from `products`
where exists (
        select * from `plans`
        where `products`.`id` = `plans`.`product_id`
          and `type` = 'off' 
          and `plans`.`deleted_at` is null
          and id in (select max(id) from plans group by product_id)
  ) 
  and `products`.`deleted_at` is null

但如果是我，我可能会编写这样的原始查询:

$wonder_product = Product::hydrateRaw('
    select products.*
    from products
    where 'off' = (
      select plans.type
      from plans
      where plans.product_id = products.id
        and plans.deleted_at is null
      order by plans.id desc
      limit 1
    )
    and products.deleted_at is null
');