PROSAGA码农传奇-Mongodb-MongoDB $集合[重复]

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  <P>
    你需要记住的一件事是
    <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/" rel="nofollow noreferrer">
      $查找
    </A>
     回报
     <code>
      zoneInfo
    </code>
     作为一个数组，所以为了使用你需要运行的那个字段
    <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/unwind/index.html" rel="nofollow noreferrer">
      $开卷
    </A>
     在上面。然后，您可以使用简单地重塑您的文档
    <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/addFields/index.html" rel="nofollow noreferrer">
      $ addFields
    </A>
     和
    <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/project/index.html" rel="nofollow noreferrer">
      $项目
    </A>
    。尝试：
  </p>
   <pre>
    <code>
      db.names.aggregate([
    {
        $lookup: {
            from: "phones",
            localField: "info.phone",
            foreignField: "phone",
            as: "phoneDetails"
        }
    },
    {
        $unwind: "$phoneDetails"
    },
    {
        $addFields: {
            "info.timezone": "$phoneDetails.timezone"
        }
    },
    {
        $project: {
            phoneDetails: 0
        }
    }
])

</code>
  </pre>
  <P>
    在最后一步中，您可以添加
    <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/out/index.html" rel="nofollow noreferrer">
      $出
    </A>
     如果要更新现有集合。
  </p>
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