MongoDB聚合组

我在mongodb中存储了如下文档：

{
  _id: ObjectId("abc"),
  teams: [{
    _id: ObjectId("aaa"),
    points: 10
  }, {
    _id: ObjectId("bbb"),
    points: 20
  }],
  players: [{
    hints: 2,
    team: ObjectId("aaa")
  }, {
    hints: 3,
    team: ObjectId("bbb")
  }]
}

给定一组文档，我想提取团队积分及其球员提示的总和。基本上，我想得到如下结果：

[{
  team: aaa,
  points: 10,
  hints: 2
}, {
  team: bbb,
  points: 20,
  hints: 3
}]

其中，points是团队在每个文档中获得的“点数”的总和，“提示”是其参与者获得的提示的总和。 我可以通过两个查询实现这一点：

db.data.aggregate([ {$unwind: { "$players" }, 
                    {$group: { _id: "$players.team", hints: { $sum: "$player.hints" } } }])

---

有没有办法只用一个查询就可以做到这一点？

您的两个查询是正确的，您可以使用它在一个查询中应用它们。在这之后，您需要对数组进行压缩，然后根据团队id展开和分组

问题是：

db.collection.aggregate([
  {
    $facet: {
      "points": [
        {
          $unwind: "$teams"
        },
        {
          $group: {
            _id: "$teams._id",
            points: {
              $sum: "$teams.points"
            }
          }
        },

      ],
      "hints": [
        {
          $unwind: "$players"
        },
        {
          $group: {
            _id: "$players.team",
            hints: {
              $sum: "$players.hints"
            }
          }
        }
      ]
    }
  },
  {
    $project: {
      merged: {
        $concatArrays: [
          "$points",
          "$hints"
        ]
      }
    }
  },
  {
    $unwind: "$merged"
  },
  {
    $group: {
      _id: "$merged._id",
      points: {
        $max: "$merged.points"
      },
      hints: {
        $max: "$merged.hints"
      }
    }
  }
])

它将输出您想要的内容

db.data.aggregate([ {$unwind: { "$teams" }, 
                    {$group: { _id: "$teams._id", points: { $sum: "$teams.points" } } }])

[{ team: aaa, points: 10 },{ team: bbb, points: 20 }]

db.collection.aggregate([
  {
    $facet: {
      "points": [
        {
          $unwind: "$teams"
        },
        {
          $group: {
            _id: "$teams._id",
            points: {
              $sum: "$teams.points"
            }
          }
        },

      ],
      "hints": [
        {
          $unwind: "$players"
        },
        {
          $group: {
            _id: "$players.team",
            hints: {
              $sum: "$players.hints"
            }
          }
        }
      ]
    }
  },
  {
    $project: {
      merged: {
        $concatArrays: [
          "$points",
          "$hints"
        ]
      }
    }
  },
  {
    $unwind: "$merged"
  },
  {
    $group: {
      _id: "$merged._id",
      points: {
        $max: "$merged.points"
      },
      hints: {
        $max: "$merged.hints"
      }
    }
  }
])