remove

Remove one or multiple documents from MongoDB collection

Syntax

n = remove(conn,collection,mongoquery)

Description

n = remove(conn,collection,mongoquery) returns the number of documents removed from a collection using the MongoDB^® connection. Use a MongoDB query to specify removing one or multiple documents.

Examples

Remove Documents Using MongoDB Query

Connect to MongoDB and remove documents from a collection. Specify a MongoDB query to determine which documents to remove. Here, the collection represents employee data.

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 MongoDB query to identify documents to remove. Here, specify the employee collection. Create the MongoDB query to identify documents in the Sales department.

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

Remove documents using the MongoDB query. The remove function removes six documents from the collection.

n = remove(conn,collection,mongoquery)

n =

     6

Close the MongoDB connection.

close(conn)

Remove All Documents from Collection

Connect to MongoDB and remove all documents from 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.

Remove all documents from the employee collection. Use an empty MongoDB query to specify removing all documents. The remove function removes three documents from the collection.

collection = "employee";
n = remove(conn,collection,"{}")

n =

     3

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 — Number of documents removed

numeric scalar

Number of documents removed from a collection in the database, returned as a numeric scalar.