Hello World

目标

通过 mongosh Shell 和 Python/PyMongo 完成 MongoDB 数据库创建、集合操作、文档 CRUD 和聚合管道。

环境准备

mongosh mongodb://localhost:27017
# 或 Docker：
docker exec -it mongo-dev mongosh

第一步：mongosh Shell 方式

// 切换到测试数据库（不存在则自动创建）
use hello_mongo

// 直接插入文档 = 隐式创建集合
db.users.insertMany([
  {
    name: "张三",
    age: 21,
    email: "zhangsan@example.com",
    hobbies: ["编程", "篮球"],
    address: { city: "北京", district: "海淀" }
  },
  {
    name: "李四",
    age: 22,
    email: "lisi@example.com",
    hobbies: ["编程", "摄影", "旅行"],
    address: { city: "上海", district: "浦东" }
  }
])

// 查询
db.users.find({ age: { $gte: 21 } })
db.users.findOne({ "address.city": "北京" })

// 投影（只返回部分字段）
db.users.find({}, { name: 1, email: 1, _id: 0 })

// 更新
db.users.updateOne(
  { name: "张三" },
  { $set: { age: 22 }, $push: { hobbies: "摄影" } }
)

// 条件更新
db.users.updateMany(
  { "address.city": "北京" },
  { $set: { "address.country": "中国" } }
)

// 删除
db.users.deleteOne({ name: "李四" })

第二步：聚合管道

// 统计各城市用户数
db.users.aggregate([
  { $group: { _id: "$address.city", count: { $sum: 1 } } },
  { $sort: { count: -1 } }
])

// 展开数组统计最受欢迎爱好
db.users.aggregate([
  { $unwind: "$hobbies" },
  { $group: { _id: "$hobbies", count: { $sum: 1 } } },
  { $sort: { count: -1 } }
])

第三步：Python PyMongo 方式

pip install pymongo

from pymongo import MongoClient

client = MongoClient("mongodb://localhost:27017")
db = client["hello_mongo"]
col = db["products"]

# 创建索引
col.create_index("name", unique=True)

# 插入
products = [
    {"name": "机械键盘", "price": 299, "tags": ["外设", "办公"], "stock": 50},
    {"name": "无线鼠标", "price": 89, "tags": ["外设", "移动"], "stock": 200},
]
col.insert_many(products)

# 查询
for p in col.find({"price": {"$lt": 300}}).sort("price", -1):
    print(f"{p['name']}: ¥{p['price']} (库存:{p['stock']})")

# 聚合：各标签商品数
pipeline = [
    {"$unwind": "$tags"},
    {"$group": {"_id": "$tags", "count": {"$sum": 1}}}
]
for r in col.aggregate(pipeline):
    print(f"标签[{r['_id']}]: {r['count']}件商品")

# 更新
col.update_one(
    {"name": "机械键盘"},
    {"$set": {"price": 259}, "$inc": {"stock": -1}}
)

client.close()

预期输出

# mongosh find
{
  _id: ObjectId("..."),
  name: '张三',
  age: 22,
  email: 'zhangsan@example.com',
  hobbies: ['编程', '篮球', '摄影']
}

# Python
机械键盘: ¥299 (库存:50)
无线鼠标: ¥89 (库存:200)
标签[外设]: 2件商品
标签[办公]: 1件商品
标签[移动]: 1件商品