Question

假设我有一个Group和Student模型，这是一对多关系；

Group具有许多Student，每个Student具有id和tuition属性。

所以我想让Group包含学生人数和所有学费。

这是我的代码：

Group::with(['student'=>function($query){
        $query->select(DB::raw('count(`id`) as numbers, sum(tuition) as total')); 
    }])->paginate(10);

它不起作用，我尝试打印sql和sql：

select count(id) as numbers, sum(tuition) as total from `group` where `student`.`group_id` in (`1`, `2`, `4`, `5`, `6`, `7`, `8`, `11`, `12`, `13`, `14`)

在mysql中运行原始sql时，我可以得到结果，但是laravel不返回有关count或sum的任何信息。

Answer 1

使用withCount()代替with()：

Group::withCount([
    'student as numbers',
    'student as total' => function($query) {
        $query->select(DB::raw('sum(tuition)'));
    }
])->paginate(10);

Laravel 5.2解决方案：

Group::selectRaw('(select count(*) from students where groups.id = students.group_id) as numbers')
    ->selectRaw('(select sum(tuition) from students where groups.id = students.group_id) as total')
    ->paginate(10);

Answer 2

您可以使用withCount()代替with()

https://laravel.com/docs/5.5/eloquent-relationships#counting-related-models

Answer 3

测试了很多；

当我使用find时，仅获得一行。

Group::with(['student'=>function($query){
    $query->select(DB::raw(' group_id ,count(`id`) as number, sum(tuition) as total')); 
}])->find(1);

有效。

我唯一想念的是我需要选择student.group_id，这意味着foreign key与hasMany的关系。

但是当您想使用paginate或get方法来获取多行时。

您只会在第一个模型对象中获得总计结果，而其他对象则为空。

        {
            "id": 1,
            "name":"first",
            "student": [
                {

                    "group_id": 1,
                    "number": 129,
                    "total": "38700.00"
                }
            ]
        },
        {
            "id": 2,
            "name":"second",
            "student": []
        },
        {
            "id": 3,
            "name":"third",
            "student": []
        },

只需添加->groupBy('group_id)，您就会得到想要的内容

 Group::with(['student'=>function($query){
    $query->select(DB::raw('id, class_id ,count(`id`) as numbers, sum(tuition) as total'))->groupBy('group_id'); 
}])->paginate(10);

结果：

 {
            "id": 1,
            "name":"first",
            "student": [
                {

                    "group_id": 1,
                    "number": 40,
                    "total": "12000.00"
                }
            ]
        },
        {
            "id": 2,
            "name":"second",
            "student": [
                {

                    "group_id": 2,
                    "number": 43,
                    "total": "12900.00"
                }

                       ]
        },
        {
            "id": 3,
            "name":"third",
            "student": [
               {

                    "group_id": 3,
                    "number": 46,
                    "total": "13800.00"
                }
             ]
        },

laravel使用关系关闭

3 个答案: