How to group data using mongo-template

问题

I have to filter data based on a criteria and set a field isObtained true or false. Then I am trying to group the data based on field grade. This is my data:

{
  "school": "xyz",
  "studentName": "John Doe",
  "grade": "first",
  "Hobbies": [
    "Painting",
    "Singing"
  ],
  "language": [
    "English"
  ],
"sport": "Badminton",
  "totalStudyHours": 85
},
{
  "school": xyz,
  "studentName": "Jane Doe",
  "grade": "third",
  "Hobbies": [
    "Painting",
    
  ],
  "language": [
    "Spanish"
  ],
"sport": "Karate",
  "totalStudyHours": 65
},
{
  "school": "xyz",
  "studentName": "joey",
  "grade": "first",
  "Hobbies": [
    "Singing"
  ],
  "language": [
    "English",
    "Italian"
  ],
"sport": "Cricket",
  "totalStudyHours": 75,
  "ispassed": true,
  
},
{
  "studentName": "jason",
  "grade": "third",
  "Hobbies": [
    "Painting",
    
  ],
  "language": [
    "English",
    "Spanish"
  ],
  "sport": "Tennis",
  "totalStudyHours": 95,
  "isObtained": true
},
{
  "studentName": "mike",
  "grade": "third",
  "Hobbies": [
    "Singing"
  ],
  "language": [
    "English",
    "Italian"
  ],
  "sport": "Badminton",
  "totalStudyHours": 70,
  "isObtained": true
}

The expected output is

[
  {
    "grade": "first",
    "values": [
      {
        "studentName": "John Doe",
        "grade": "first",
        "Hobbies": [
          "Painting",
          "Singing"
        ],
        "language": [
          "English"
        ],
        "sport": "Badminton",
        "totalStudyHours": 85,
        "isObtained": true
      },
      {
        "studentName": "joey",
        "grade": "first",
        "Hobbies": [
          "Singing"
        ],
        "language": [
          "English",
          "Italian"
        ],
        "sport": "Cricket",
        "totalStudyHours": 75,
        "isObtained": true
      }
    ]
  },
  {
    "grade": "third",
    "values": [
      {
        "studentName": "jason",
        "grade": "third",
        "Hobbies": [
          "Painting",
          
        ],
        "language": [
          "English",
          "Spanish"
        ],
        "sport": "Tennis",
        "totalStudyHours": 95,
        "isObtained": true
      },
      {
        "studentName": "mike",
        "grade": "third",
        "Hobbies": [
          "Singing"
        ],
        "language": [
          "English",
          "Italian"
        ],
        "sport": "Badminton",
        "totalStudyHours": 70,
        "isObtained": true
      }
    ]
  }
]

In the mongoDb query, the isObtained field is set based on what field we want. For example, if we want records with sport as "Badminton" then the isObtained field will be true when sport is Badminton and false otherwise.

Here is the query, but I am facing problem in grouping based on grade.

db.students.aggregate([
  {
    "$match": {
      "$and": [
        {
          "school": "xyz"
        }
      ]
    }
  },
  {
    "$project": {
      "sport": 1,
      "language": 1,
      "hobbies": 1,
      "isObtained": {
        "$and": [
          {
            "$eq": [
              "$sport",
              "Badminton"
            ]
          }
        ]
      }
    }
  }

回答1:

• $match your conditions
• $group by grade and make array of root documents in values,
• define required fields and check condition created field isObtained if sport is Badminton then true otherwise false

db.students.aggregate([
  { $match: { school: "xyz" } },
  {
    $group: {
      _id: "$grade",
      values: {
        $push: {
          sport: "$sport",
          language: "$language",
          Hobbies: "$Hobbies",
          isObtained: {
            $cond: [{ $eq: ["$sport", "Badminton"] }, true, false]
          }
        }
      }
    }
  }
])

Playground

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If you want to go with dynamic approach then try $mergeObjects with $$ROOT,

Playground

来源：https://stackoverflow.com/questions/65914720/how-to-group-data-using-mongo-template