db={"Employee":[{"id":"5f474ebb12a55e2a1c4fb39f","emp_status":true,"logAttendance":true,"createdAt":"2020-08-27T06:09:31.533Z","empId":"10000","firstName":"firstName","lastName":"lastName","gender":"male","dob":"2020-07-11T08:53:20.691Z","email":"abcd@abcd.com","department":{"_id":"5f2f8599e5f4c015e4827c3f","departmentName":"department","organizationName":"department ",},"designation":{"_id":"5f2f85b2e5f4c015e4827c42","designationName":"designation "}}],"Attendance":[{"_id":"5f4a05bb09f14077c82157bb","empId":"10000","employee":"5f474ebb12a55e2a1c4fb39f","weekOff":false,"dated":"2020-08-29T07:37:31.525Z","inTime":"2020-08-29T04:30:08.000Z","outTime":"2020-08-30T15:30:25.000Z"}]}

db.Attendance.aggregate([{$group:{_id:"$employee",attendance:{$push:"$$ROOT"},},},{$unwind:"$attendance"},{$lookup:{from:"Employee",localField:"attendance.employee",foreignField:"id",as:"employeeData",},}])