使用 mongoose 计算 mongodb 中子文档的数据答案

【问题标题】：Count data from subdocuments in mongodb with mongoose使用 mongoose 计算 mongodb 中子文档的数据
【发布时间】：2016-11-30 21:13:27
【问题描述】：

我正在尝试使用嵌套子文档对数据进行计数，但我无法理解如何获得我想要的（如果可能的话）。

我有以下用于约会列表的猫鼬模式：

var AppointmentSchema = new mongoose.Schema(
	{
		clinic: {
			type: mongoose.Schema.Types.ObjectId, 
			ref: 'Clinic',
			required: true,
		},
		type: {
			type: mongoose.Schema.Types.ObjectId, 
			ref: 'AppointmentType',
			required: true,
		}
	}
);

var ClinicSchema = new mongoose.Schema(
	{
		name: {
			type: String,
			maxlength: 25,
			required: true,
		}
	}
);

var AppointmentTypeSchema = new mongoose.Schema(
	{
		name: {
			type: String,
			minlength: 2,
			maxlength: 25,
			required: true,
		}
	}
);

从预约列表中，我希望报告指标以了解每个诊所不同类型预约的数量。

到目前为止，无论诊所使用以下聚合，我都只能获得每种预约类型的计数：

db.appointments.aggregate(
    [
        {
            $group: {
                _id: '$type',  //$type is the column name in collection
                count: {$sum: 1}
            }
        },
        {
            $sort: { count: -1 }
        }
    ]
);

这将返回以下结果：

{ "_id" : ObjectId("5838ef21b19aee730b8ae6c8"), "count" : 5 }
{ "_id" : ObjectId("5838efa4d695cb7839672417"), "count" : 3 }
{ "_id" : ObjectId("5838efb4d695cb7839672419"), "count" : 3

但我想得到如下：

{
	{
		id: 1,
		name: "Name of the clinic #1",
		count: [
			{
				id: 10,
				name: "Appointment Type #10",
				count: 4,
			},
			{
				id: 20,
				name: "Appointment Type #20",
				count: 1,
			}
		]
	},
	{
		id: 2,
		name: "Name of the clinic #2",
		count: [
			{
				id: 10,
				name: "Appointment Type #10",
				count: 5,
			},
			{
				id: 20,
				name: "Appointment Type #20",
				count: 2,
			}
		]
	}
}

【问题讨论】：

标签： mongodb mongoose-schema

【解决方案1】：

下面的聚合查询会给你类似的结果：

db.appointments.aggregate(
    [
        {
            $group: {
                _id: "$clinic",
                count: { $push: "$type" }
            }

        },
        {
            $project:{
                _id: 0,
                id: "$_id._id",
                name: "$_id.name",
                "count": 1
            }
        }
    ]
).pretty();

示例输出：

{
        "count" : [
                {
                        "_id" : ObjectId("583ecd06401ce04a0ca7e170"),
                        "name" : "Appointment Type 1"
                },
                {
                        "_id" : ObjectId("583ecd09401ce04a0ca7e171"),
                        "name" : "Appointment Type 2"
                },
                {
                        "_id" : ObjectId("583ecd0c401ce04a0ca7e172"),
                        "name" : "Appointment Type 3"
                }
        ],
        "id" : ObjectId("583eccf6401ce04a0ca7e16d"),
        "name" : "Clinic 1"
}
{
        "count" : [
                {
                        "_id" : ObjectId("583ecd06401ce04a0ca7e170"),
                        "name" : "Appointment Type 1"
                },
                {
                        "_id" : ObjectId("583ecd0c401ce04a0ca7e172"),
                        "name" : "Appointment Type 3"
                }
        ],
        "id" : ObjectId("583eccfd401ce04a0ca7e16e"),
        "name" : "Clinic 2"
}
{
        "count" : [
                {
                        "_id" : ObjectId("583ecd06401ce04a0ca7e170"),
                        "name" : "Appointment Type 1"
                }
        ],
        "id" : ObjectId("583ecd01401ce04a0ca7e16f"),
        "name" : "Clinic 3"
}

count 中的 count: 4 与什么相关？

【讨论】：