Find the MongoDB document from sub array?

You can use dot(.) notation to find the document from sub array. Let us first create a collection with documents −

> db.findDocumentDemo.insertOne(
...    {
...       "EmployeeDetails" :
...       {
...          "EmployeeAppraisalTime":
...
...          [
...
...             {"EmployeeDesignation": "Developer", "Salary": 45000},
...             {"EmployeeDesignation": "Tester", "Salary": 30000},
...             {"EmployeeDesignation": "HR", "Salary": 22000},
...             {"EmployeeDesignation": "Accountant", "Salary": 18000}
...          ]
...       }
...    }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd2c0f7b64f4b851c3a13a8")
}
> db.findDocumentDemo.insertOne(
...    {
...       "EmployeeDetails" :
...       {
...          "EmployeeAppraisalTime":
...
...          [
...
...             {"EmployeeDesignation": "Developer", "Salary": 105000},
...             {"EmployeeDesignation": "Tester", "Salary": 45000},
...             {"EmployeeDesignation": "HR", "Salary": 34000},
...             {"EmployeeDesignation": "Accountant", "Salary": 24000}
...          ]
...       }
...    }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd2c1d5b64f4b851c3a13a9")
}

Following is the query to display all documents from a collection with the help of find() method −

> db.findDocumentDemo.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5cd2c0f7b64f4b851c3a13a8"),
   "EmployeeDetails" : {
      "EmployeeAppraisalTime" : [
         {
            "EmployeeDesignation" : "Developer",
            "Salary" : 45000
         },
         {
            "EmployeeDesignation" : "Tester",
            "Salary" : 30000
         },
         {
            "EmployeeDesignation" : "HR",
            "Salary" : 22000
         },
         {
            "EmployeeDesignation" : "Accountant",
            "Salary" : 18000
         }
      ]
   }
}
{
   "_id" : ObjectId("5cd2c1d5b64f4b851c3a13a9"),
   "EmployeeDetails" : {
      "EmployeeAppraisalTime" : [
         {
            "EmployeeDesignation" : "Developer",
            "Salary" : 105000
         },
         {
            "EmployeeDesignation" : "Tester",
            "Salary" : 45000
         },
         {
            "EmployeeDesignation" : "HR",
            "Salary" : 34000
         },
         {
            "EmployeeDesignation" : "Accountant",
            "Salary" : 24000
         }
      ]
   }
}

Following is the query to find document from sub array −

> db.findDocumentDemo.find({ 'EmployeeDetails.EmployeeAppraisalTime.EmployeeDesignation': 'Developer', 'EmployeeDetails.EmployeeAppraisalTime.Salary': { '$in': [45000,105000] } } );

This will produce the following output −

{ "_id" : ObjectId("5cd2c0f7b64f4b851c3a13a8"), "EmployeeDetails" : { "EmployeeAppraisalTime" : [ { "EmployeeDesignation" : "Developer", "Salary" : 45000 }, { "EmployeeDesignation" : "Tester", "Salary" : 30000 }, { "EmployeeDesignation" : "HR", "Salary" : 22000 }, { "EmployeeDesignation" : "Accountant", "Salary" : 18000 } ] } }

{ "_id" : ObjectId("5cd2c1d5b64f4b851c3a13a9"), "EmployeeDetails" : { "EmployeeAppraisalTime" : [ { "EmployeeDesignation" : "Developer", "Salary" : 105000 }, { "EmployeeDesignation" : "Tester", "Salary" : 45000 }, { "EmployeeDesignation" : "HR", "Salary" : 34000 }, { "EmployeeDesignation" : "Accountant", "Salary" : 24000 } ] } }