Match ID and fetch documents with $eq in MongoDB in case of array?

Use $eq operator along with find() to match ID and fetch documents. The $eq specifies equality condition. It matches documents where the value of a field equals the specified value.

Let us create a collection with documents −

> db.demo426.insert({"Ids":["110","120","101"]});
WriteResult({ "nInserted" : 1 })
> db.demo426.insert({"Ids":["100","201","401"]});
WriteResult({ "nInserted" : 1 })
> db.demo426.insert({"Ids":["501","600","700"]});
WriteResult({ "nInserted" : 1 })

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

> db.demo426.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5e75e50fbbc41e36cc3cae72"),
   "Ids" : [
         "110",
         "120",
         "101"
      ]
   }
{
   "_id" : ObjectId("5e75e51abbc41e36cc3cae73"),
   "Ids" : [
      "100",
      "201",
      "401"
      ]
   }
   {
   "_id" : ObjectId("5e75e527bbc41e36cc3cae74"),
   "Ids" : [
      "501",
      "600",
      "700"
   ]
}

Following is the query match ID with $eq in MongoDB −

> db.demo426.find({"Ids":{$eq:"501"}});

This will produce the following output −

{ "_id" : ObjectId("5e75e527bbc41e36cc3cae74"), "Ids" : [ "501", "600", "700" ] }