什么是 WhereHas Laravel 中的关系计数条件
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What is relationship count condition in WhereHas Laravel
提问by hhsadiq
I am having a difficulty understanding the relationship count condition in WhereHas. The docs page does not have discussion about it but API pagetalks about it. Quote from API.
我很难理解WhereHas 中的关系计数条件。文档页面没有讨论它，但API 页面谈论它。来自 API 的报价。
Builder|Builder whereHas(string $relation, Closure $callback, string $operator = '>=', int $count = 1)
Add a relationship count condition to the query with where clauses.
Builder|Builder whereHas(string $relation, Closure $callback, string $operator = '>=', int $count = 1)
使用 where 子句向查询添加关系计数条件。
Example
例子
A ResourceModel has Many to Many relation to ResourceCategory
一个Resource模型具有多对多关系ResourceCategory
public function categories()
{
return $this->belongsToMany('ResourceCategory', 'resource_category_mapping');
}
Relationship condition in Has
Has中的关系条件
The relationship condition in Hasis working as expected.
Has 中的关系条件按预期工作。
Resource::has('categories', '>', 1)->get()
//this return all resources which have more than one catgories
Relationship condition in WhereHas
WhereHas 中的关系条件
The relationship condition in WhereHas is not working as expected. I am sure I have misunderstood it.
WhereHas 中的关系条件未按预期工作。我确定我误解了它。
Resource::whereHas('categories', function ( $query){
$query->whereIn('resource_category_id', [1, 2, 4]);
}, '>', 1)->get()
The above code should return resources which whose categories belong to either of [1, 2, 4] and the resource has more than one categories. But it is not.
上面的代码应该返回类别属于 [1, 2, 4] 之一的资源，并且该资源有多个类别。但事实并非如此。
Question
题
Kindly explain the relationship condition in WhereHas, may be providing an example would be much helpful.
请解释WhereHas中的关系条件，可能提供一个例子会很有帮助。
回答by jedrzej.kurylo
Normally, whereHas()checks if your model has at least onerelated model. You can set $countto some higher value to increase the count to Nand fetch only the models that have at least Nrelated models.
通常，whereHas() 会检查您的模型是否至少有一个相关模型。您可以将$count设置为更高的值以将计数增加到N并仅获取至少具有N 个相关模型的模型。
In your case, calling
在你的情况下，打电话
Resource::has('categories', '>', 2)->get();
will return only those Resourcesthat have at least 2related categories.
将返回只有那些资源具有至少2个相关类别。
