The MongoDB Query Language comes with a powerful combination of query commands.

Count Queries

The following two commands both retrieve the count of the filtered documents:

db.collection.count( <filter>, <options> )
db.collection.countDocuments( <filter>, <options> )

If the result does not need to be accurate and can be estimated, the following command can be used:

db.collection.estimatedDocumentCount( <options> )

Simple Queries

When simple queries need to be executed, the following command can be used:

db.collection.find( <filter>, <projection> )

To number of retrieved records can also directly be limited to one:

db.collection.findOne( <filter>, <projection> )

Complex Queries

Complex queries can be constructed using the aggregation pipeline

db.collection.aggregate( <pipeline>, <options> )