Database
[{"sCode":"1010","PCode":"1011","category":"Diagnostic","procedure":"Oral assessment for patients up to the age of 3 years inclusive. ","serviceClassification":"First Dental Visit/Orientation",},{"sCode":"1100","PCode":"1101","category":"Diagnostic","procedure":"Examination and Diagnosis, Complete, Primary Dentition","serviceClassification":"Examinations, And Diagnosis Complete Oral",},{"sCode":"1100","PCode":"1102","category":"Diagnostic","procedure":"Examination and Diagnosis, Complete, Mixed Dentition","serviceClassification":"Examinations, And Diagnosis Complete Oral",},{"sCode":"1100","PCode":"1103","category":"Diagnostic","procedure":"Examination and Diagnosis, Complete, Permanent Dentition","serviceClassification":"Examinations, And Diagnosis Complete Oral",},{"sCode":"1200","PCode":"1201","category":"Diagnostic","procedure":"Examination and Diagnosis, Limited, Oral, New Patient. Examination and diagnosis of hard and soft","serviceClassification":"Examinations And Diagnosis, Limited Oral",},{"sCode":"1200","PCode":"1202","category":"Diagnostic","procedure":"Examination and diagnosis, Limited oral, Previous Patient (recall). Examination of hard and soft","serviceClassification":"Examinations And Diagnosis, Limited Oral",},{"sCode":"98100","PCode":"98101","category":"Adjunctive General Services","procedure":"One unit of time","serviceClassification":"Counseling, Tobacco-Use Cessation Services",},{"sCode":"98100","PCode":"98102","category":"Adjunctive General Services","procedure":"Two units of time","serviceClassification":"Counseling, Tobacco-Use Cessation Services",},{"sCode":"98100","PCode":"98109","category":"Adjunctive General Services","procedure":"Each additionial unit of time","serviceClassification":"Counseling, Tobacco-Use Cessation Services",}]
Query
db.collection.aggregate([{$group:{_id:{serviceClassification:"$serviceClassification",category:"$category"},children:{$push:"$$ROOT"}}},{$group:{_id:"$_id.category",children:{$push:{"_id":{$toUpper:"$_id.serviceClassification"},"children":"$children"}}}}])