MongoDB query to fetch only the “Name” field based on roles?

For this, use aggregate(). Here, we have considered 3 roles − Admin, Guest, and User. Let us create a collection with documents −

> db.demo532.insertOne({"Name":"Chris","Type":"Admin"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e8b4a9def4dcbee04fbbbf9")
}
> db.demo532.insertOne({"Name":"David","Type":"Guest"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e8b4aa3ef4dcbee04fbbbfa")
}
> db.demo532.insertOne({"Name":"Bob","Type":"User"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e8b4ab0ef4dcbee04fbbbfb")
}

Display all documents from a collection with the help of find() method −

> db.demo532.find();

This will produce the following output −

{ "_id" : ObjectId("5e8b4a9def4dcbee04fbbbf9"), "Name" : "Chris", "Type" : "Admin" }
{ "_id" : ObjectId("5e8b4aa3ef4dcbee04fbbbfa"), "Name" : "David", "Type" : "Guest" }
{ "_id" : ObjectId("5e8b4ab0ef4dcbee04fbbbfb"), "Name" : "Bob", "Type" : "User" }

Following is the query to get a unique document which needs to be compared with other documents in the same collection −

> db.demo532.aggregate([
...    {$group: {_id:"$Name", "types":{$addToSet:"$Type"}}},
...    {$project: {_id:1, "types": 1, "isSubset": { $setIsSubset: [ ["Admin"], "$types" ] }}},
...    {$match: {"isSubset": false}},
...    {$group: {_id:"$isSubset", "Name": {$push : "$_id"}}},
...    {$project: {"_id": 0, "Name": 1}},
...    {$unwind: "$Name"}
... ])

This will produce the following output −

{ "Name" : "David" }
{ "Name" : "Bob" }

AmitDiwan

Published on 14-May-2020 06:22:34

• Related Questions & Answers
• Query MongoDB with “like” implementation on name and email field beginning with a specific letter?
• MongoDB regular expression to fetch record with specific name “John”, instead of “john”
• MongoDB Query for boolean field as “not true”
• Should I name the username field in my MySQL table “name” or “user_name”?
• “Toggle” query in MongoDB?
• MongoDB query to search for string like “@email” in the field values
• How to query MongoDB with “like”?
• MongoDB query to filter only the logs containing the “work” word in the content
• MySQL query to fetch only a single field on the basis of boolean value in another field
• How to query MongoDB similar to “like” ?
• Find the MongoDB collection size for name “Chris”
• Querying only the field name and display only the id in MongoDB?
• MongoDB “$and” operator for subcollection to fetch a document?
• “Structured” grouping query in MongoDB to display result with a new field displaying the count
• Can we use the “.” symbol in MongoDB collection name?