如何查询嵌套数组？

嵌套数组是指数组中包含另一个数组。在查询嵌套数组时，我们需要使用嵌套数组的层级结构。下面是一些示例代码，用于查询嵌套数组。

假设我们有以下数据：

{
  "name": "John Doe",
  "addresses": [
    {
      "street": "123 Main St",
      "city": "Big City",
      "state": "CA",
      "zip": "12345"
    },
    {
      "street": "456 Second St",
      "city": "Small Town",
      "state": "CA",
      "zip": "67890"
    }
  ]
}

要查询 John Doe 的第一个地址，可以使用以下代码：

db.collection.find({name: "John Doe"}, {"addresses.0": 1})

这将返回以下文档：

{
  "_id": ObjectId("621c80171f3d36255ae1de6b"),
  "name": "John Doe",
  "addresses": [
    {
      "street": "123 Main St",
      "city": "Big City",
      "state": "CA",
      "zip": "12345"
    }
  ]
}

要查询所有州是 “CA” 的地址，可以使用以下代码：

db.collection.find({"addresses.state": "CA"})

这将返回以下两个文档：

{
  "_id": ObjectId("621c80171f3d36255ae1de6b"),
  "name": "John Doe",
  "addresses": [
    {
      "street": "123 Main St",
      "city": "Big City",
      "state": "CA",
      "zip": "12345"
    },
    {
      "street": "456 Second St",
      "city": "Small Town",
      "state": "CA",
      "zip": "67890"
    }
  ]
}

{
  "_id": ObjectId("621c804b1f3d36255ae1de6c"),
  "name": "Jane Smith",
  "addresses": [
    {