[
  {
    "_id": {
      "$oid": "5f5f280ffa2236115655cb6a"
    },
    "Name": "Rovilio Chipman",
    "Last_season": {
      "year": "2010-2011",
      "goals": 10,
      "assists": 1
    },
    "Last_season_2": {
      "year": "2011-2012",
      "goals": 1,
      "assists": 12
    },
    "Seasons": [
      {
        "year": "2012-2013",
        "goals": 11,
        "assists": 4
      },
      {
        "year": "2013-2014",
        "goals": 6,
        "assists": 2
      },
      {
        "year": "2014-2015",
        "goals": 5,
        "assists": 5
      }
    ]
  }
]

首先，您需要将所有值放入一个数组中，然后可以计算平均值。这可能是一个解决方案：
    db.collection.aggregate([
      {
        $set: {
          AllSeasons: {
            $concatArrays: [
              "$Seasons",
              [ "$Last_season" ],
              [ "$Last_season_2" ]
            ]
          }
        }
      },
      { $set: { average: { $avg: [ "$AllSeasons.goals" ] } } },
      { $unset: "AllSeasons" }
    ])

<details>
<summary>英文:</summary>
First you need to put all values in one array, then you can calculate the average. This could be one solution:
    db.collection.aggregate([
      {
        $set: {
          AllSeasons: {
            $concatArrays: [
              &quot;$Seasons&quot;,
              [ &quot;$Last_season&quot; ],
              [ &quot;$Last_season_2&quot; ]
            ]
          }
        }
      },
      { $set: { average: { $avg: [ &quot;$AllSeasons.goals&quot; ] } } },
      { $unset: &quot;AllSeasons&quot; }
    ])
[Mongo Playground][1]
  [1]: https://mongoplayground.net/p/QLsvSsBoAGz
</details>
# 答案2
**得分**: 1
你可以使用Mongo聚合来实现这个。
```json
db.collection.aggregate([
  {
    "$project": {
      /* 在Seasons列表中求目标之和 */
      "seasons_goals": { 
        "$sum": [
          "$Seasons.goals"
        ]
      },
      /* 计算季节数量：Seasons的长度 + 2 */
      "nb_seasons": {
        "$sum": [
          {
            "$size": "$Seasons"
          },
          2
        ]
      },
      /* 求最后两个季节的目标之和 */
      "total": {
        "$sum": [
          "$Last_season.goals",
          "$Last_season_2.goals"
        ]
      }
    }
  },
  /* 通过将seasons_goals+total除以nb_seasons来计算平均值 */
  {
    "$project": {
      "result": {
        "$divide": [
          {
            "$sum": [
              "$seasons_goals",
              "$total"
            ]
          },
          "$nb_seasons"
        ]
      }
    }
  }
])

[
  {
    "$set": {
      "Seasons": {
        "$concatArrays": [
          "$Seasons",
          [
            "$Last_season_2",
            "$Last_season"
          ]
        ]
      }
    }
  },
  {
    "$project": {
      "Name": 1,
      "avgGoals": {
        "$divide": [
          {
            "$reduce": {
              "input": "$Seasons",
              "initialValue": 0,
              "in": {
                "$sum": [
                  "$$this.goals",
                  "$$value"
                ]
              }
            }
          },
          {
            "$size": "$Seasons"
          }
        ]
      }
    }
  }
]