如何根据特定键获取 MongoDB 中的最大值和最小值？

我想获得 emp 的最大值和最小值salary基于currency。每个员工的薪资范围基于currency此外，响应中的所有详细信息都应该是唯一的。虽然我使用聚合函数 min 和 max 但它获取工资金额的最大值和最小值，但我需要根据currency field.

样本数据：

[
  {
    "id": "1",
    "emp_name": "emp1",
    "data": [
      {
        "emp_country": "country1",
        "emp_city": "city1",
        "salary": [
          {
            "currency": "INR",
            "amount": 5000
          },
          {
            "currency": "INR",
            "amount": 600
          },
          {
            "currency": "MXN",
            "amount": 400
          }
        ]
      },
      {
        "emp_country": "country1",
        "emp_city": "city2",
        "salary": [
          {
            "currency": "DOLLER",
            "amount": 5000
          },
          {
            "currency": "DOLLER",
            "amount": 200
          },
          {
            "currency": "MXN",
            "amount": 400
          }
        ]
      }
    ]
  },
  {
    "id": "2",
    "emp_name": "emp2",
    "data": [
      {
        "emp_country": "country2",
        "emp_city": "city2",
        "salary": [
          {
            "currency": "INR",
            "amount": 5000
          },
          {
            "currency": "MXN",
            "amount": 200
          },
          {
            "currency": "MXN",
            "amount": 400
          }
        ]
      }
    ]
  },
  {
    "id": "3",
    "emp_name": "emp3",
    "data": [
      {
        "emp_country": "country1",
        "emp_city": "city1",
        "salary": [
          {
            "currency": "MXN",
            "amount": 400
          }
        ]
      }
    ]
  },
  {
    "id": "4",
    "emp_name": "emp4",
    "data": [
      {
        "emp_country": "country1",
        "emp_city": "city2",
        "salary": [
          {
            "currency": "DOLLER",
            "amount": 200
          }
        ]
      }
    ]
  }
]

预期输出： 城市，国家，名称应该是唯一的，工资有基于货币的最大和最小。

[
  {
    "emp_city": "city1",
    "emp_country": "country1",
    "emp_name": "emp1",
    "emp_salary": [{
      "currency": "INR",
      "max": 5000,
      "min": 600
    },
    {
      "currency": "MXN",
      "max": 400,
      "min": 400
    }]
  },
  {
    "emp_city": "city2",
    "emp_country": "country1",
    "emp_name": "emp1",
    "emp_salary":[ {
      "currency": "DOLLER",
      "max": 5000,
      "min": 200
    },
    {
      "currency": "MXN",
      "max": 400,
      "min": 400
    }]
  },
  {
    "emp_city": "city2",
    "emp_country": "country2",
    "emp_name": "emp2",
    "emp_salary": [{
      "currency": "INR",
      "max": 5000,
      "min": 5000
    },
    {
      "currency": "MXN",
      "max": 400,
      "min": 200
    }]
  },
  {
    "emp_city": "city1",
    "emp_country": "country1",
    "emp_name": "emp3",
    "emp_salary": [{
      "currency": "MXN",
      "max": 400,
      "min": 400
    }]
  },
  {
    "emp_city": "city2",
    "emp_country": "country1",
    "emp_name": "emp4",
    "emp_salary": [{
      "currency": "DOLLER",
      "max": 200,
      "min": 200
    }]
  }
]

我们可以使用聚合查询来实现上述结果。

• $unwind- 解构工资数组
• $group- 按雇员城市、国家、姓名、货币以及工资的最小值和最大值进行分组
• $group- 使用另一个推入 emp_salary
• $project- 以您的格式显示字段

db.collection.aggregate([
  {
    "$unwind": {
      "path": "$data"
    }
  },
  {
    "$unwind": {
      "path": "$data.salary"
    }
  },
  {
    "$group": {
      "_id": {
        "emp_city": "$data.emp_city",
        "emp_country": "$data.emp_country",
        "emp_name": "$emp_name",
        "currency": "$data.salary.currency",
        
      },
      "max": {
        "$max": "$data.salary.amount"
      },
      "min": {
        "$min": "$data.salary.amount"
      }
    }
  },
  {
    "$group": {
      "_id": {
        "emp_city": "$_id.emp_city",
        "emp_country": "$_id.emp_country",
        "emp_name": "$_id.emp_name",
        
      },
      "emp_salary": {
        "$push": {
          "currency": "$_id.currency",
          "min": "$min",
          "max": "$max"
        }
      }
    }
  },
  {
    "$project": {
      "_id": 0,
      "emp_city": "$_id.emp_city",
      "emp_country": "$_id.emp_country",
      "emp_name": "$_id.emp_name",
      "emp_salary": 1,
      
    }
  }
])

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