MongoDB Essential Commands

  • Inserting a new field in to existing collection
	db.collection1.update({},{$set : {"newfield":1}},false,true)

In the above command, newfield (value = 1) is inserted in the collection - collection 1

  • How to find unique values. Lets say we want to find unique values for "field1"
  • How to find by field1 and find unique values for field2
docs = db.collection1.find('field2',{'field1':<val>})

Result - docs is a list of values of field2

  • How to find values using regex

Put your value inside the two forward slashes as shown below...

		docs = db.collection1.find({'field1':/<val>/})

To ignore case use "i" after the 2nd forward slash

		docs = db.collection1.find({'field1':/<val>/i})
  • How to update fields with null values

Lets say for a field "package" we want to update the value where 'package" value is null across all the documents in db

db.collection1.update( { "package" : null }, { $set:{ "package" : -1 } }, { multi : true } );

Above command will update the value of "package" whereever it is null to -1 for all the documents.

  • How to rename a field in mongoDB

Lets say we want to update field "package" to "pkg". Use the following command...

db.collection1.update({}, {$rename:{"package":"pkg"}}, false, true)
  • How to do find documents with logical OR and AND

Above command will find all the documents where package is not equal to empty "AND" not equal to null

We can also use the above command with distinct.


Above command will find all the unique packages where package is not equal to empty "AND" not equal to null