MongoDB聚合与列表数据

Question

我需要使用 mongodb 聚合将数据与一组字段分组。这是我在集合中的数据

[
    {
        bookName: "aaaa",
        bookNo: "1",
        registeredDate: "2018-02-01T06:51:16.738Z"
    },
    {
        bookName: "bbbb",
        bookNo: "2",
        registeredDate: "2018-02-01T06:51:29.244Z"
    }
    {
        bookName: "cccc",
        bookNo: "1",
        registeredDate: "2018-02-01T06:51:29.244Z"
    }
    {
        bookName: "dddd",
        bookNo: "2",
        registeredDate: "2018-02-01T06:51:29.244Z"
    }
]

我需要将上面的数据聚合成group by，并显示组内的数据。这是我需要的输出，

{
    Books: [
        {
        bookNo: "1",
            books: [{
                    bookName: "aaaa",
                    registeredDate: "2018-02-01T06:51:16.738Z"
                },
                {
                    bookName: "cccc",
                    registeredDate: ""2018-02-01T06:51:29.244Z"
                }]
        },
        {
        bookNo: "2",
            books: [{
                bookName: "bbbb",
                registeredDate: "2018-02-01T06:51:29.244Z"
            },
            {
                bookName: "dddd",
                registeredDate: "2018-02-01T06:51:29.244Z"
            }]
        }
    ]
}

有人帮我找到解决办法。

提前致谢，

Answer 1

尝试以下聚合：

db.books.aggregate([
    {
        $group: {
            _id: "$bookNo",
            books: {
                $push: {
                    bookName: "$bookName",
                    registeredDate: "$registeredDate"
                }
            }
        }
    },
    {
        $project:{
            _id: 0,
            bookNo: "$_id",
            books: 1
        }
    }
])

在$group 中，您可以指定每个文档中哪些字段将是$pushed。然后您可以使用$project 将_id 重命名为bookNo 字段

Answer 2

db.collection.aggregate(

    // Pipeline
    [
        // Stage 1
        {
            $group: {
                _id: '$bookNo',
                //Books:{$addToSet:{bookNo:'$bookNo'}},
                books: {
                    $addToSet: {
                        bookname: '$bookName',
                        registeredDate: '$registeredDate'
                    }
                },

            }
        },

        // Stage 2
        {
            $group: {
                _id: null,
                Books: {
                    $addToSet: {
                        books: '$books',
                        bookNo: '$_id'
                    }
                }
            }
        },

        // Stage 3
        {
            $project: {
                _id: 0,
                Books: 1
            }
        }

    ]


);