find
Description
returns all documents in a collection by using the MongoDB® C++ interface connection.documents
= find(conn
,collection
)
specifies additional options using one or more name-value arguments. For example,
documents
= find(conn
,collection
,Name=Value
)Limit=10
limits the number of documents returned to
10.
Examples
Retrieve All Documents in Collection
Connect to MongoDB® using the MongoDB C++ interface, retrieve all documents in a collection, and import them into MATLAB®. In this example, each document in the collection represents an employee.
Create a MongoDB connection to the database mongotest
using the MongoDB C++ interface. Here, the database server dbtb01
hosts this database using port number 27017
.
server = "dbtb01"; port = 27017; dbname = "mongotest"; conn = mongoc(server,port,dbname)
conn = connection with properties:
Database: "mongotest"
UserName: ""
Server: "dbtb01"
Port: 27017
CollectionNames: [13×1 string]
conn
is the connection
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 13 document collections.
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.
Specify the employees
collection for document retrieval. Retrieve all documents in the collection by using the MongoDB connection. documents
is a cell array of structures.
collection = "employees";
documents = find(conn,collection);
Display the first document in the collection. Each document is a structure.
documents{1}
ans = struct with fields:
_id: '5d8ccb9c961c96252819ea63'
employee_id: 100
first_name: 'Steven'
last_name: 'King'
email: 'SKING'
phone_number: '515.123.4567'
hire_date: '2003-06-17 00:00:00.0'
job_id: 'AD_PRES'
salary: 24000
department_id: 90
temporary: 0
The structure fields are:
Unique identifier
Employee identifier
First name
Last name
Email
Phone number
Hire date
Job name
Employee salary
Department identifier
Temporary flag
Close the MongoDB connection.
close(conn)
Retrieve All Documents in MongoDB Query
Connect to MongoDB® using the MongoDB C++ interface, retrieve all documents in a MongoDB query on a collection in the database, and import them into MATLAB®. In this example, each document in the collection represents an employee.
Create a MongoDB connection to the database mongotest
using the MongoDB C++ interface. Here, the database server dbtb01
hosts this database using port number 27017
.
server = "dbtb01"; port = 27017; dbname = "mongotest"; conn = mongoc(server,port,dbname)
conn = connection with properties:
Database: "mongotest"
UserName: ""
Server: "dbtb01"
Port: 27017
CollectionNames: [13×1 string]
conn
is the connection
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 13 document collections.
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.
Specify the employees
collection for document retrieval. Create the MongoDB query as a string scalar that contains a JSON-style string. This query retrieves all employees in the department that has the department identifier 80
.
collection = "employees"; mongoquery = "{""department_id"":80}";
Retrieve all documents in the MongoDB query on the employees
collection by using the MongoDB connection. documents
is a cell array that contains a structure for each document returned by the query.
documents = find(conn,collection,Query=mongoquery);
Close the MongoDB connection.
close(conn)
Sort Retrieved Documents in Collection
Connect to MongoDB® using the MongoDB C++ interface and retrieve documents in a MongoDB query on a collection in the database. Then, sort the results by a field in the documents. In this example, each document in the collection represents an employee.
Create a MongoDB connection to the database mongotest
using the MongoDB C++ interface. Here, the database server dbtb01
hosts this database using port number 27017
.
server = "dbtb01"; port = 27017; dbname = "mongotest"; conn = mongoc(server,port,dbname)
conn = connection with properties:
Database: "mongotest"
UserName: ""
Server: "dbtb01"
Port: 27017
CollectionNames: [13×1 string]
conn
is the connection
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 13 document collections.
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.
Specify the employees
collection for document retrieval. Create the MongoDB query as a string scalar that contains a JSON-style string. This query retrieves all employees in the department that has the department identifier 80
.
collection = "employees"; mongoquery = "{""department_id"":80}";
Create the sort query as a string scalar that contains a JSON-style string. Sort the documents by the salary field.
sortquery = "{""salary"":1.0}";
Retrieve all documents in the MongoDB query on the employees
collection by using the MongoDB connection, and sort the documents. documents
is a cell array that contains a structure for each document returned by the query. The documents are sorted by salary in increasing order.
documents = find(conn,collection,Query=mongoquery,Sort=sortquery);
Display the data for the first two employees sorted by salary. The salary for the second employee is higher than the first employee.
documents{1:2}
ans = struct with fields:
_id: '5d8ccc16961c96252819ea68'
employee_id: 148
first_name: 'Gerald'
last_name: 'Cambrault'
email: 'GCAMBRAU'
phone_number: '011.44.1344.619268'
hire_date: '2007-10-15 00:00:00.0'
job_id: 'SA_MAN'
salary: 11000
commission_pct: 0.3000
manager_id: 100
department_id: 80
temporary: 0
ans = struct with fields:
_id: '5d8ccc12961c96252819ea67'
employee_id: 147
first_name: 'Alberto'
last_name: 'Errazuriz'
email: 'AERRAZUR'
phone_number: '011.44.1344.429278'
hire_date: '2005-03-10 00:00:00.0'
job_id: 'SA_MAN'
salary: 12000
commission_pct: 0.3000
manager_id: 100
department_id: 80
temporary: 0
Close the MongoDB connection.
close(conn)
Retrieve Specific Fields in Collection
Connect to MongoDB® using the MongoDB C++ interface and retrieve all documents in a collection. Specify the fields to retrieve for each document. Import the documents into MATLAB®. In this example, each document in the collection represents an employee.
Create a MongoDB connection to the database mongotest
using the MongoDB C++ interface. Here, the database server dbtb01
hosts this database using port number 27017
.
server = "dbtb01"; port = 27017; dbname = "mongotest"; conn = mongoc(server,port,dbname)
conn = connection with properties:
Database: "mongotest"
UserName: ""
Server: "dbtb01"
Port: 27017
CollectionNames: [13×1 string]
conn
is the connection
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 13 document collections.
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.
Specify the employees
collection for document retrieval. Specify the fields to retrieve for each document by using a string scalar that contains a JSON-style string. For this example, return the department_id
and salary
fields.
collection = "employees"; fields = "{""department_id"":1.0,""salary"":1.0}";
Retrieve all documents in the collection. Use the name-value argument Projection
to retrieve the specified fields for each document. documents
is a cell array.
documents = find(conn,collection,Projection=fields);
Display the first document in the results. In addition to the unique identifier for the document, the document contains only the specified fields.
documents{1}
ans = struct with fields:
_id: '5d8ccb9c961c96252819ea63'
salary: 24000
department_id: 90
Close the MongoDB connection.
close(conn)
Retrieve Specific Number of Documents Using Offset
Connect to MongoDB® using the MongoDB C++ interface and retrieve a specific number of documents in a collection in the database. Return documents from a specific position in the results using an offset value. Import the documents into MATLAB®. In this example, each document in the collection represents an employee.
Create a MongoDB connection to the database mongotest
using the MongoDB C++ interface. Here, the database server dbtb01
hosts this database using port number 27017
.
server = "dbtb01"; port = 27017; dbname = "mongotest"; conn = mongoc(server,port,dbname)
conn = connection with properties:
Database: "mongotest"
UserName: ""
Server: "dbtb01"
Port: 27017
CollectionNames: [13×1 string]
conn
is the connection
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 13 document collections.
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.
Specify the employees
collection for document retrieval.
collection = "employees";
Use the name-value argument Skip
to skip the first five documents in the collection. Then, use the name-value argument Limit
to return the next 10 documents in the collection. documents
is a cell array that contains 10 documents.
documents = find(conn,collection,Skip=5,Limit=10);
Close the MongoDB connection.
close(conn)
Input Arguments
conn
— MongoDB C++ interface connection
connection
object
MongoDB C++ interface connection, specified as a connection
object.
collection
— Collection name
string scalar
Collection name, specified as a string scalar.
Example: "taxidata"
Data Types: string
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Example: Skip=5,Limit=10
skips the first five documents in a
collection and returns the next 10 documents.
Query
— 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: Query="{""department"":""Sales""}"
queries
the database for documents where the department
field
is equal to Sales
.
Example: Query="{""salary"": {""$gt"": 90000}}"
queries the database for documents where the value of the
salary
field is greater than
90000
.
Example: Query="{""_id"":{""$oid"":""593fec95b78dc311e01e9204""}}"
queries the database for the document that has the identifier
593fec95b78dc311e01e9204
.
Data Types: char
| string
Projection
— Fields
string scalar | character vector
Fields to retrieve in each document, specified as a string scalar or character vector. Specify a JSON-style string to describe the fields.
Example: Projection="{""department"":1.0,""salary"":1.0}"
returns the department
and salary
fields.
Data Types: char
| string
Sort
— Sort field
string scalar | character vector
Sort field for documents, specified as a string scalar or character vector. Specify a JSON-style string to describe the sort field.
Example: Sort="{""department"":1.0}"
sorts the
returned documents by the department
field.
Data Types: char
| string
Skip
— Offset
numeric scalar
Offset from the beginning of the returned documents, specified as a numeric scalar.
Example: Skip=5
skips the first five returned
documents.
Data Types: double
Limit
— Number of documents to return
numeric scalar
Number of documents to return, specified as a numeric scalar.
Example: Limit=10
returns 10
documents.
Data Types: double
Output Arguments
documents
— Documents
structure | structure array | cell array of structures
Documents in a MongoDB collection or query on a collection, returned as a structure, structure array, or cell array of structures.
Each JSON-style document is represented as a structure. The
find
function returns a:
Structure for one document
Structure array for multiple documents containing the same fields
Cell array of structures for multiple documents containing different fields
Version History
Introduced in R2021b
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