Mongodb - 子文档键的正则表达式匹配

Mongodb是一种流行的NoSQL数据库，它以其灵活的数据模型和强大的查询功能而备受开发者的喜爱。在Mongodb中，文档可以包含子文档，这些子文档可以用于存储更复杂的数据结构。而使用正则表达式来匹配Mongodb中的子文档键是一种常见的需求。

json
{
  "name": "John",
  "address": {
    "street": "123 Main St",
    "city": "New York"
  }
}
{
  "name": "Alice",
  "address": {
    "street": "456 Elm St",
    "city": "Los Angeles"
  }
}
{
  "name": "Bob",
  "address": {
    "street": "789 Oak St",
    "city": "San Francisco"
  }
}

python
import pymongo
# 连接到Mongodb数据库
client = pymongo.MongoClient("mongodb://localhost:27017/")
db = client["mydatabase"]
users = db["users"]
# 查询所有具有以"city"开头的子文档键的文档
query = { "address": { "$regex": "^city" } }
results = users.find(query)
# 输出查询结果
for result in results:
  print(result)

json
{
  "_id": ObjectId("5f5d8c2e30d4a7f7eabfbddc"),
  "name": "John",
  "address": {
    "street": "123 Main St",
    "city": "New York"
  }
}
{
  "_id": ObjectId("5f5d8c2e30d4a7f7eabfbddd"),
  "name": "Alice",
  "address": {
    "street": "456 Elm St",
    "city": "Los Angeles"
  }
}
{
  "_id": ObjectId("5f5d8c2e30d4a7f7eabfbdde"),
  "name": "Bob",
  "address": {
    "street": "789 Oak St",
    "city": "San Francisco"
  }
}