如何在 mongo 中使用 groupby 以及包含字符串的 addFields？

Question

我在 mongo 集合中有四个字段 Sender、Recipient、Credit、Debit。其中 Credit 和 Debit 是字符串形式的数字。我需要根据Sender、Recipient 进行分组并添加Credit、Debit 的整数值，并根据贷方和借方的净值对结果进行排序

我有这样的数据库

Sender   Recipient  Credit  Debit
“Mike”   “John”      “600”   “-300” 
“Alis”   “Ajay”      “300”   “-800” 
“Arun”   “Ankit”     “360”   “-300” 
“Mike”    “Cris”      “0”    “-100”       

我需要这样的结果

Sender   Recipient  NetAmount
“Mike”    “John”        “300” 
Arun”     “Ankit”       “-60”
“Mike”    “Cris”        “-100”       
“Alis”    “Ajay”        “-500”

我试过这样做

DataModel.aggregate([
      {
        $group: {
          _id: {
            sender: '$ sender,
            recipient: '$recipient',
          },
        },
      },
      {
        $project: {
          credit: '$credit.creditAmount,
          debit: '$debit.debitAmount,
        },
      }, {
        $addFields: {
          netAmount: {
            $add: [{ $toInt: '$ credit }, { $toInt: '$ debit }],
          },
        }
      },
    ]);

但它没有给出预期的结果。

Answer 1

• $group by Sender and Recipient, sum Credit and Debit 使用 $toInt 转换为整数后的数量
• $project 显示必填字段并使用 $add 对 Credit 和 Debit 字段求和
• $match 检查NetAmount 不为零
• $sort NetAmount 按降序排列

db.collection.aggregate([
  {
    $group: {
      _id: {
        Sender: "$Sender",
        Recipient: "$Recipient"
      },
      Credit: { $sum: { $toInt: "$Credit" } },
      Debit: { $sum: { $toInt: "$Debit" } }
    }
  },
  {
    $project: {
      _id: 0,
      Sender: "$_id.Sender",
      Recipient: "$_id.Recipient",
      NetAmount: { $add: ["$Credit", "$Debit"] }
    }
  },
  { $match: { NetAmount: { $ne: 0 } } },
  { $sort: { NetAmount: -1 } }
])

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