distinct

Retrieve distinct values for field in MongoDB collection

Syntax

values = distinct(conn,collection,field)

values = distinct(conn,collection,field,'Query',mongoquery)

Description

values = distinct(conn,collection,field) returns distinct values for a field in a collection by using the MongoDB^® connection.

values = distinct(conn,collection,field,'Query',mongoquery) returns distinct values for a field in an executed MongoDB query on a collection.

Examples

Retrieve Distinct Values for Field in Collection

Connect to MongoDB and retrieve a distinct set of values for a field in a collection of documents. 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.

Retrieve a distinct set of values for a field in a document collection. Here, retrieve distinct salaries for all employees. values is a cell array of doubles.

collection = "employee";
field = "salary";
values = distinct(conn,collection,field);

Display the first three salaries in the cell array.

values{1:3}

ans =

       60000


ans =

       50000


ans =

       55000

Close the MongoDB connection.

close(conn)

Retrieve Distinct Values for Field in MongoDB Query

Connect to MongoDB and retrieve a distinct set of values for a field in a MongoDB query. 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 retrieve a distinct set of values for a field. Here, retrieve distinct salaries of all employees in the Sales department. values is a cell array of doubles.

collection = "employee";
field = "salary";
values = distinct(conn,collection,field,'Query',mongoquery)

values =

  1×3 cell array

    {[60000]}    {[64440]}    {[66000]}

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

field — Field

string scalar

Field in a collection, specified as a string scalar.

Example: "department"

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

values — Distinct values

cell array

Distinct values of a field in a MongoDB collection or query, specified as a cell array. The cell array can contain numeric scalars for numeric data, character vectors for text data, and structures for nested documents.