Find in mongodb example
Collections can be queried with find. The result for the query is actually a cursor object. This can be used directly or converted to an array. To indicate which fields must or must no be returned fields value can be used. For example the following fields value.
MongoDB Driver Quick Start
Note The following code snippets come from the QuickTour. MongoDB Driver. See Installation for instructions on how to install the MongoDB driver. The MongoClient instance represents a pool of connections to the database; you will only need one instance of class MongoClient even with multiple threads.
However, if you do create multiple instances:. All resource usage limits e. The following example shows five ways to connect to the database mydb on the local machine. If the database does not exist, MongoDB will create it for you. The connection string mostly follows RFC , with the exception of the domain name. For MongoDB, it is possible to list multiple domain names separated by a comma. For more information on the connection string, see connection string. Specify the name of the database to the getDatabase method.
If a database does not exist, MongoDB creates the database when you first store data for that database. Once you have a MongoDatabase instance, use its getCollection method to access a collection. Specify the name of the collection to the getCollection method. If a collection does not exist, MongoDB creates the collection when you first store data for that collection. For example, using the database instance, the following statement accesses the collection named test in the mydb database:.
To create the document using the Java driver, use the Document class. To create the document using the Java driver, instantiate a Document object with a field and value, and use its append method to include additional fields and values to the document object.
The value can be another Document object to specify an embedded document:. Once you have the MongoCollection object, you can insert documents into the collection. To insert these documents to the collection, pass the list of documents to the insertMany method. The following code should print the inserted via insertMany plus the 1 inserted via the insertOne.
You can call the method without any arguments to query all documents in a collection or pass a filter to query for documents that match the filter criteria. The find method returns a FindIterable instance that provides a fluent interface for chaining other methods. To return the first document in the collection, use the find method without any parameters and chain to find method the first method.
To retrieve all the documents in the collection, we will use the find method without any parameters. To iterate through the results, chain the iterator method to the find. The following example retrieves all documents in the collection and prints the returned documents documents :.
Although the following idiom for iteration is permissible, avoid its use as the application can leak a cursor if the loop terminates early:. To to query for documents that match certain conditions, pass a filter object to the find method. To facilitate creating filter objects, Java driver provides the Filters helper. For example, to find the first document where the field i has the value 71 , pass an eq filter object to specify the equality condition:. The example uses the forEach method on the FindIterable object to apply a block to each document.
A filter object to determine the document or documents to update. To specify an empty filter i. An update document that specifies the modifications. For a list of the available operators, see update operators. The update methods return an UpdateResult which provides information about the operation including the number of documents modified by the update. To update at most a single document, use the updateOne. The following example updates the first document that meets the filter i equals 10 and sets the value of i to :.
To update all documents matching the filter, use the updateMany method. Pass to the methods a filter object to determine the document or documents to delete. The delete methods return a DeleteResult which provides information about the operation including the number of documents deleted.
To delete at most a single document that match the filter, use the deleteOne method:. The following example deletes at most one document that meets the filter i equals :.
To delete all documents matching the filter use the deleteMany method. The following example deletes all documents where i is greater or equal to :. To create an index on a field or fields, pass an index specification document to the createIndex method. An index key specification document contains the fields to index and the index type for each field:. For a list of other index types, see Create Indexes. For additional tutorials such as to use the aggregation framework, specify write concern, etc.
Version Select Version. However, if you do create multiple instances: All resource usage limits e. To dispose of an instance, call MongoClient.
MongoDB Find and Distinct
We at Exploratory use MongoDB quite a lot. However, as you would imagine, that might not be always efficient or even practical sometimes due to the time it takes to download the data and the memory size limit of your PC. There are a few things you need to know before proceeding further. The data looks something like below. And it looks like below in Table view in Exploratory.
One of the most important operations in any kind of database is retrieving data. Data can be retrieved all at once or filtered. MongoDB provides the find operation to retrieve data. The data is stored in documents, which in turn are stored in collections. By default, the find operation will retrieve all the documents in a collection.
This page documents the mongo shell method, and does not refer to the MongoDB Node. Selects documents in a collection or view and returns a cursor to the selected documents. The projection parameter determines which fields are returned in the matching documents. The projection parameter takes a document of the following form:. Expression using a Projection Operators. Executing db. Type it to continue iteration.
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There are totally six methods available in Mongo DB by which we can fetch particular records. Find method consists of two parameters by which we can fetch a particular record. If we don't use these two parameters then the find method will return all the documents available within the MongoDB collection. Query — This is an optional parameter which defines the selection criteria. In simple words, what you want to search within a collection will be defined as a query.
If you do something in the MongoDB shell and you would like to translate it to Perl, the best way is to run the function in the shell without parentheses, which will print the source. You can then generally translate the source into Perl fairly easily. The find-one-and-modify commands in MongoDB::Collection are similar to update or remove , but will return the modified document. They can be useful for implementing queues or locks.
An Introduction to MongoDB Query for Beginners
Documentation Help Center. Retrieve documents in MongoDB collection. For example, 'Limit',10 limits the number of documents returned toSEE VIDEO BY TOPIC: MongoDB Queries (Part 4) - Filter/Search Documents
There are two ways to find an item from the MongoDB database. One is through MongoDB find method and the other is through findOne method. MongoDB find method fetches the document in a collection and returns the cursor for the documents matching the criteria requested by the user. The syntax for mongodb find method is as follows db. For example: db.
MongoDB Query Document using find() with Example
Note The following code snippets come from the QuickTour. MongoDB Driver. See Installation for instructions on how to install the MongoDB driver. The MongoClient instance represents a pool of connections to the database; you will only need one instance of class MongoClient even with multiple threads. However, if you do create multiple instances:. All resource usage limits e. The following example shows five ways to connect to the database mydb on the local machine.
The method of fetching or getting data from a MongoDB database is carried out by using queries. MongoDB provides a function called db. During the course of this tutorial, you will see how this function is used in various ways to achieve the purpose of document retrieval. Basic query operations The basic query operations cover the simple operations such as getting all of the documents in a MongoDB collection.
In MongoDB we use the find and findOne methods to find data in a collection. To select data from a collection in MongoDB, we can use the findOne method. The findOne method returns the first occurrence in the selection.
MongoDB Query Document Using Find() Method (Examples)
MongoDB - Query Document