count

Count total number of documents in MongoDB collection

Syntax

n = count(conn,collection)

n = count(conn,collection,'Query',mongoquery)

Description

n = count(conn,collection) returns the total number of documents in a collection by using the MongoDB^® connection.

n = count(conn,collection,'Query',mongoquery) returns the total number of documents in an executed MongoDB query on a collection.

Examples

Count Documents in Collection

Connect to MongoDB and count the total number of documents in a collection.

Create a MongoDB connection to the database mongotest. Here, the database server dbtb01 hosts this database using port number 27017.

server = "dbtb01";
port = 27017;
dbname = "mongotest";
conn = mongo(server,port,dbname)

conn = 

  mongo with properties:

               Database: 'mongotest'
               UserName: ''
                 Server: {'dbtb01'}
                   Port: 27017
        CollectionNames: {'airlinesmall', 'employee', 'largedata' ... and 3 more}
         TotalDocuments: 23485919

conn is the mongo object that contains the MongoDB connection. The object properties contain information about the connection and the database.

• The database name is mongotest.

• The user name is blank.

• The database server is dbtb01.

• The port number is 27017.

• This database contains six document collections. The first three collection names are airlinesmall, employee, and largedata.

• This database contains 23,485,919 documents.

Verify the MongoDB connection.

isopen(conn)

ans =

  logical

   1

The database connection is successful because the isopen function returns 1. Otherwise, the database connection is closed.

Determine the number of documents in the employee collection. The collection contains 25 documents.

collection = "employee";
n = count(conn,collection)

n =

    25

Close the MongoDB connection.

close(conn)

Count Documents in MongoDB Query

Connect to MongoDB and count the total number of documents in a MongoDB query on a collection in the database. Here, each document in the collection represents an employee.

Create a MongoDB connection to the database mongotest. Here, the database server dbtb01 hosts this database using port number 27017.

server = "dbtb01";
port = 27017;
dbname = "mongotest";
conn = mongo(server,port,dbname)

conn = 

  mongo with properties:

               Database: 'mongotest'
               UserName: ''
                 Server: {'dbtb01'}
                   Port: 27017
        CollectionNames: {'airlinesmall', 'employee', 'largedata' ... and 3 more}
         TotalDocuments: 23485919

conn is the mongo object that contains the MongoDB connection. The object properties contain information about the connection and the database.

• The database name is mongotest.

• The user name is blank.

• The database server is dbtb01.

• The port number is 27017.

• This database contains six document collections. The first three collection names are airlinesmall, employee, and largedata.

• This database contains 23,485,919 documents.

Verify the MongoDB connection.

isopen(conn)

ans =

  logical

   1

The database connection is successful because the isopen function returns 1. Otherwise, the database connection is closed.

Create a JSON-style query as a character vector that contains a JSON-style string. This query sets the department field equal to the value Sales.

mongoquery = '{"department":"Sales"}';

Use the MongoDB query on the employee collection to count the total number of employees who work in the Sales department. A total of four employees work in the Sales department.

collection = "employee";
n = count(conn,collection,'Query',mongoquery)

n =

     4

Close the MongoDB connection.

close(conn)

Input Arguments

conn — MongoDB connection

mongo object

MongoDB connection, specified as a mongo object.

collection — Collection name

string scalar

Collection name, specified as a string scalar.

Example: "taxidata"

Data Types: string

mongoquery — MongoDB query

string scalar | character vector

MongoDB query, specified as a string scalar or character vector. Specify a JSON-style string to query the database.

Example: '{"department":"Sales"}' queries the database for documents where the department field is equal to Sales.

Example: '{salary: {$gt: 90000}}' queries the database for documents where the value of the salary field is greater than 90000.

Data Types: char | string

Output Arguments

n — Total number of documents

numeric scalar

Total number of documents in a MongoDB collection or query, returned as a numeric scalar.