Laravel 雄辩的计数关系

2021-12-26 00:00:00 php laravel eloquent

我是 laravel 和 eloquent 的新手，我不确定这是否可能.但我有 2 张表具有一对多的关系.一种是位置"，一种是用户".一个位置可以有多个用户.

I'm new to laravel and eloquent and I'm not sure if this is even possible. but I have 2 tables with a one to many relationship. One is "locations" and one is "users". One location can have many users.

因此，如果我想获取所有用户的所有位置，我会这样做:

So if I wanted to get all locations with all users I would just do this:

Location::with("users")->get();

但我也想知道每个位置有多少用户，我尝试这样做

But I also want to know how many users each location has, I tried doing this

Location::with("users")->count("users")->get();

但这没有用.

推荐答案

如果您使用预先加载，则不会出现提到的 n+1 问题.

The n+1 issue that was mentioned doesn't occur if you use eager loading.

$locations = Location::with('users')->get();

$locations->users()->count();

无论您有多少用户或位置，这都会产生三个查询.

This should result in three queries, no matter how many users or locations you have.

  • 对位置模型进行计数查询
  • 从位置选择 *
  • select * from users where in

混淆是因为这也有效:

$locations = Location::all();

$locations->users()->count();

但在这种情况下，它会为每个位置查询一次.

But in this case, it does query once for each location.

查看文档了解更多信息:http://laravel.com/docs/eloquent#eager-loading

See the docs for more info: http://laravel.com/docs/eloquent#eager-loading

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