Find documents which contain a particular value in MongoDB using Regular Expressions?

To find documents containing a particular value with Regular Expressions, use MongoDB $regex. Let us create a collection with documents −

> db.demo469.insertOne({"StudentName":"John Doe"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e80532fb0f3fa88e227906b")
}
> db.demo469.insertOne({"StudentName":"Chris Brown"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e80533ab0f3fa88e227906c")
}
> db.demo469.insertOne({"StudentName":"John Smith"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e805341b0f3fa88e227906d")
}
> db.demo469.insertOne({"StudentName":"Jace Doe"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e805347b0f3fa88e227906e")
}
> db.demo469.insertOne({"StudentName":"David Miller"});{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e80534eb0f3fa88e227906f")
}

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

> db.demo469.find();

This will produce the following output −

{ "_id" : ObjectId("5e80532fb0f3fa88e227906b"), "StudentName" : "John Doe" }
{ "_id" : ObjectId("5e80533ab0f3fa88e227906c"), "StudentName" : "Chris Brown" }
{ "_id" : ObjectId("5e805341b0f3fa88e227906d"), "StudentName" : "John Smith" }
{ "_id" : ObjectId("5e805347b0f3fa88e227906e"), "StudentName" : "Jace Doe" }
{ "_id" : ObjectId("5e80534eb0f3fa88e227906f"), "StudentName" : "David Miller" }

Following is the query to find documents which contain a particular value in MongoDB −

> db.demo469.find({'StudentName': {'$regex':'john', '$options':'i'}});

This will produce the following output −

{ "_id" : ObjectId("5e80532fb0f3fa88e227906b"), "StudentName" : "John Doe" }
{ "_id" : ObjectId("5e805341b0f3fa88e227906d"), "StudentName" : "John Smith" }