demo_10_01 云数据库聚合_addFields_01 连续两次addFields

数据表：

{

    "scores": { // 集合（表名）

        "data": [ // 数据

            {

                "_id": 1,

                "student": "Maya",

                "homework": [10, 5, 10],

                "quiz": [10, 8],

                "extraCredit": 0

            },

            {

                "_id": 2,

                "student": "Ryan",

                "homework": [5, 6, 5],

                "quiz": [8, 8],

                "extraCredit": 8

            }

        ]

    }

}

 

聚合操作：

'use strict';

const db = uniCloud.database();

const $ = db.command.aggregate;

exports.main = async(event, context) => {

    const msg = db.collection('scores').aggregate()

        // 添加两个字段:

        .addFields({

            totalHomework: $.sum('$homework'),

            totalQuiz: $.sum('$quiz')

        })

        // 根据上面新添加的两个字段值在添加一个字段

        .addFields({

            totalScore: $.add(['$totalHomework', '$totalQuiz', '$extraCredit'])

        })

        .end();

    return msg;

};

// 聚合之后的返回值

/*

{

    "affectedDocs": 2,

    "data": [{

        "_id": 1,

        "extraCredit": 0,

        "homework": [10, 5, 10],

        "quiz": [10, 8],

        "student": "Maya",

        "totalHomework": 25,

        "totalQuiz": 18,

        "totalScore": 43

    }, {

        "_id": 2,

        "extraCredit": 8,

        "homework": [5, 6, 5],

        "quiz": [8, 8],

        "student": "Ryan",

        "totalHomework": 16,

        "totalQuiz": 16,

        "totalScore": 40

    }]

}

*/