mongo Shell Quick Reference

Start mongo shell without connecting to a database.

To connect later, see Opening New Connections.

Used in conjunction with a JavaScript file (i.e. <file.js>) to continue in the mongo shell after running the JavaScript file.

See JavaScript file for an example.

Print a list of all databases on the server.

The operation corresponds to the listDatabases command. If the deployment runs with access control, the operation returns different values based on user privileges. See listDatabases Behavior for details.

Print a list of all collections for current database.

Print a list of all available databases.

The operation corresponds to the listDatabases command. If the deployment runs with access control, the operation returns different values based on user privileges. See listDatabases Behavior for details.

Set a specific collection in the current database to a variable coll, as in the following example:

coll = db.myCollection;

You can perform operations on the myCollection using the variable, as in the following example:

coll.find();

Find all documents in the collection and returns a cursor.

See the db.collection.find() and Query Documents for more information and examples.

See Iterate a Cursor in mongosh for information on cursor handling in the mongo shell.

Find the documents matching the <query> criteria in the collection. If the <query> criteria is not specified or is empty (i.e {} ), the read operation selects all documents in the collection.

The following example selects the documents in the users collection with the name field equal to "Joe":

coll = db.users;
coll.find( { name: "Joe" } );

For more information on specifying the <query> criteria, see Specify Equality Condition.

Find documents matching the <query> criteria and return just specific fields in the <projection>.

The following example selects all documents from the collection but returns only the name field and the _id field. The _id is always returned unless explicitly specified to not return.

coll = db.users;
coll.find( { }, { name: true } );

For more information on specifying the <projection>, see Project Fields to Return from Query.

Return results in the specified <sort order>.

The following example selects all documents from the collection and returns the results sorted by the name field in ascending order (1). Use -1 for descending order:

coll = db.users;
coll.find().sort( { name: 1 } );

Returns the total number of documents that match the query.

The count() ignores limit() and skip(). For example, if 100 records match but the limit is 10, count() will return 100. This will be faster than iterating yourself, but still take time.

Find and return a single document. Returns null if not found.

The following example selects a single document in the users collection with the name field matches to "Joe":

coll = db.users;
coll.findOne( { name: "Joe" } );

Internally, the findOne() method is the find() method with a limit(1).

db = connect("<host><:port>/<dbname>")

conn = new Mongo()
db = conn.getDB("dbname")

Open a connection to a new server using new Mongo().

Use getDB() method of the connection to select a database.