MongoDB使用

April 21, 2022

MongoDB 非常适合与 JavaScript 一起使用

概念

collection （可以看作 sql 的 table）

document （可以看作 sql 的 row）

每个 document 都是一个 BSON 对象（形式上类似于 JSON，或者说是 JavaScript 对象）

// 一个 document
{
    "_id": ObjectId("58904e3796f927a806a182d"),
    "name": "John",
    "age": 25,
    "email": "john@email.email",
    "language": ["C++", "Python"]
}

collection 即 document 的集合

MongoDB 支持的类型比较多，参考https://www.mongodb.com/docs/manual/reference/bson-types/

命令行

可以在 https://www.mongodb.com/docs/manual/tutorial/getting-started/ 体验 mongoDB 的 shell，它是一个 JavaScript 的 shell

db

显示当前数据库名称

use <db>

切换数据库，如果不存在则创建

db.collection.insertMany()

在指定 collection 插入多个 document

db.movies.insertMany([
    {
        title: "Titanic",
        year: 1997,
        genres: ["Drama", "Romance"],
        rated: "PG-13",
        languages: ["English", "French", "German", "Swedish", "Italian", "Russian"],
        released: ISODate("1997-12-19T00:00:00.000Z"),
        awards: {
            wins: 127,
            nominations: 63,
            text: "Won 11 Oscars. Another 116 wins & 63 nominations.",
        },
        cast: ["Leonardo DiCaprio", "Kate Winslet", "Billy Zane", "Kathy Bates"],
        directors: ["James Cameron"],
    },
    {
        title: "The Dark Knight",
        year: 2008,
        genres: ["Action", "Crime", "Drama"],
        rated: "PG-13",
        languages: ["English", "Mandarin"],
        released: ISODate("2008-07-18T00:00:00.000Z"),
        awards: {
            wins: 144,
            nominations: 106,
            text: "Won 2 Oscars. Another 142 wins & 106 nominations.",
        },
        cast: ["Christian Bale", "Heath Ledger", "Aaron Eckhart", "Michael Caine"],
        directors: ["Christopher Nolan"],
    },
    {
        title: "Spirited Away",
        year: 2001,
        genres: ["Animation", "Adventure", "Family"],
        rated: "PG",
        languages: ["Japanese"],
        released: ISODate("2003-03-28T00:00:00.000Z"),
        awards: {
            wins: 52,
            nominations: 22,
            text: "Won 1 Oscar. Another 51 wins & 22 nominations.",
        },
        cast: ["Rumi Hiiragi", "Miyu Irino", "Mari Natsuki", "Takashi Naitè"],
        directors: ["Hayao Miyazaki"],
    },
    {
        title: "Casablanca",
        genres: ["Drama", "Romance", "War"],
        rated: "PG",
        cast: ["Humphrey Bogart", "Ingrid Bergman", "Paul Henreid", "Claude Rains"],
        languages: ["English", "French", "German", "Italian"],
        released: ISODate("1943-01-23T00:00:00.000Z"),
        directors: ["Michael Curtiz"],
        awards: {
            wins: 9,
            nominations: 6,
            text: "Won 3 Oscars. Another 6 wins & 6 nominations.",
        },
        lastupdated: "2015-09-04 00:22:54.600000000",
        year: 1942,
    },
]);

db.collection.find()

javascript

// 查询所有文档
db.movies.find({});
// 查询 directors 值为 "Christopher Nolan" 的文档
db.movies.find({ directors: "Christopher Nolan" });
// 查询 released 值小于（前于）ISODate("2000-01-01") 的文档，lt = less than
db.movies.find({ released: { $lt: ISODate("2000-01-01") } });
// 查询 awards.wins 值大于 100 的文档，gt = greater than，注意此处的 awards.wins
db.movies.find({ "awards.wins": { $gt: 100 } });
// 查询 languages 包括 ["Japanese", "Mandarin"] 的文档
db.movies.find({ languages: { $in: ["Japanese", "Mandarin"] } });

指定返回字段

db.movies.find({}, { title: 1, directors: 1, year: 1 });
// 无需指定_id，因为默认就会返回，如果不需要_id，可以设置为0
db.movies.find({}, { _id: 0 });

db.collection.aggregate()

聚合查询

db.movies.aggregate([
    { $unwind: "$genres" },
    {
        $group: {
            _id: "$genres",
            genreCount: { $count: {} },
        },
    },
    { $sort: { genreCount: -1 } },
]);

详细参见文档

https://www.mongodb.com/docs/manual/crud/

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