问题描述
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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