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Find in mongoose node js

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There's some confusion on the internet about what happens when you call Model. Make no mistake, Model. But there's some confusion about Model. In this article, I'll provide a conceptual overview of what happens when you call Model. For the purposes of this article, I'll assume you already have a MongoDB instance running on localhost If you don't, check out run-rs , it downloads and runs MongoDB for you with no dependencies beyond Node.

SEE VIDEO BY TOPIC: Use mongoose and Express to Find one User using Id from the MongoDB

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It then goes on to show how we can use Mongoose to provide database access for the LocalLibrary website. It explains how object schema and models are declared, the main field types, and basic validation. It also briefly shows a few of the main ways in which you can access model data. Library staff will use the Local Library website to store information about books and borrowers, while library members will use it to browse and search for books, find out whether there are any copies available, and then reserve or borrow them.

In order to store and retrieve information efficiently, we will store it in a database. Express apps can use many different databases, and there are several approaches you can use for performing C reate, R ead, U pdate and D elete CRUD operations.

This tutorial provides a brief overview of some of the available options and then goes on to show in detail the particular mechanisms selected. While there is no single "best" database, almost any of the popular solutions should be more than acceptable for a small-to-medium-sized site like our Local Library. The very best performance can be gained by using SQL, or whatever query language is supported by the database.

ODM's are often slower because they use translation code to map between objects and the database format, which may not use the most efficient database queries this is particularly true if the ODM supports different database backends, and must make greater compromises in terms of what database features are supported.

The benefit of using an ORM is that programmers can continue to think in terms of JavaScript objects rather than database semantics — this is particularly true if you need to work with different databases on either the same or different websites.

They also provide an obvious place to perform data validation. Unless you're very familiar with the native query language or performance is paramount, you should strongly consider using an ODM. As a general rule, you should consider both the features provided and the "community activity" downloads, contributions, bug reports, quality of documentation, etc. For the Local Library example and the rest of this topic we're going to use the Mongoose ODM to access our library data.

This ODM and database combination is extremely popular in the Node community, partially because the document storage and query system looks very much like JSON, and is hence familiar to JavaScript developers. Tip: You don't need to know MongoDB in order to use Mongoose, although parts of the Mongoose documentation are easier to use and understand if you are already familiar with MongoDB.

The rest of this tutorial shows how to define and access the Mongoose schema and models for the LocalLibrary website example. Before you jump in and start coding the models, it's worth taking a few minutes to think about what data we need to store and the relationships between the different objects.

We know that we need to store information about books title, summary, author, genre, ISBN and that we might have multiple copies available with globally unique ids, availability statuses, etc. We might need to store more information about the author than just their name, and there might be multiple authors with the same or similar names.

We want to be able to sort information based on the book title, author, genre, and category. When designing your models it makes sense to have separate models for every "object" a group of related information.

In this case some obvious candidates for these models are books, book instances, and authors. You might also want to use models to represent selection-list options e. A good example is a genre e. Once we've decided on our models and fields, we need to think about the relationships between them. With that in mind, the UML association diagram below shows the models we'll define in this case as boxes. As discussed above, we've created models for the book the generic details of the book , book instance status of specific physical copies of the book available in the system , and author.

We have also decided to have a model for the genre so that values can be created dynamically. We've decided not to have a model for the BookInstance:status — we will hard code the acceptable values because we don't expect these to change. Within each of the boxes, you can see the model name, the field names and types, and also the methods and their return types.

The diagram also shows the relationships between the models, including their multiplicities. The multiplicities are the numbers on the diagram showing the numbers maximum and minimum of each model that may be present in the relationship. For example, the connecting line between the boxes shows that Book and a Genre are related. This choice was somewhat arbitrary — we could equally well have had the field in the other schema.

Note : The next section provides a basic primer explaining how models are defined and used. As you read it, consider how we will construct each of the models in the diagram above. Note: This primer is heavily influenced by the Mongoose quick start on npm and the official documentation. Mongoose is installed in your project package. To install it, use the following command inside your project folder:. If you want to install a MongoDB server then you can download installers from here for various operating systems and install it locally.

You can also use cloud-based MongoDB instances. This is suitable for development and makes sense for the tutorial because it makes "installation" operating system independent database-as-a-service is also one approach you might use for your production database.

Mongoose requires a connection to a MongoDB database. You can require and connect to a locally hosted database with mongoose. You can get the default Connection object with mongoose. Once connected, the open event is fired on the Connection instance. Tip: If you need to create additional connections you can use mongoose. This takes the same form of database URI with host, database, port, options etc.

Models are defined using the Schema interface. The Schema allows you to define the fields stored in each document along with their validation requirements and default values. In addition, you can define static and instance helper methods to make it easier to work with your data types, and also virtual properties that you can use like any other field, but which aren't actually stored in the database we'll discuss a bit further below.

Schemas are then "compiled" into models using the mongoose. Once you have a model you can use it to find, create, update, and delete objects of the given type. Note: Each model maps to a collection of documents in the MongoDB database. The code fragment below shows how you might define a simple schema.

First you require mongoose, then use the Schema constructor to create a new schema instance, defining the various fields inside it in the constructor's object parameter. In the case above we just have two fields, a string and a date. In the next sections, we will show some of the other field types, validation, and other methods. The first argument is the singular name of the collection that will be created for your model Mongoose will create the database collection for the above model SomeModel above , and the second argument is the schema you want to use in creating the model.

Note: Once you've defined your model classes you can use them to create, update, or delete records, and run queries to get all records or particular subsets of records. We'll show you how to do this in the Using models section, and when we create our views. A schema can have an arbitrary number of fields — each one represents a field in the documents stored in MongoDB. An example schema showing many of the common field types and how they are declared is shown below.

The exceptions are:. For more information about options see SchemaTypes Mongoose docs. Mongoose provides built-in and custom validators, and synchronous and asynchronous validators. The example below slightly modified from the Mongoose documents shows how you can specify some of the validator types and error messages:. For complete information on field validation see Validation Mongoose docs.

Virtual properties are document properties that you can get and set but that do not get persisted to MongoDB. The getters are useful for formatting or combining fields, while setters are useful for de-composing a single value into multiple values for storage. The example in the documentation constructs and deconstructs a full name virtual property from a first and last name field, which is easier and cleaner than constructing a full name every time one is used in a template.

For more information see Virtuals Mongoose documentation. The instance and static methods are similar, but with the obvious difference that an instance method is associated with a particular record and has access to the current object. Query helpers allow you to extend mongoose's chainable query builder API for example, allowing you to add a query "byName" in addition to the find , findOne and findById methods. Once you've created a schema you can use it to create models.

The model represents a collection of documents in the database that you can search, while the model's instances represent individual documents that you can save and retrieve. We provide a brief overview below. To create a record you can define an instance of the model and then call save. The examples below assume SomeModel is a model with a single field "name" that we have created from our schema.

Creation of records along with updates, deletes, and queries are asynchronous operations — you supply a callback that is called when the operation completes. The API uses the error-first argument convention, so the first argument for the callback will always be an error value or null.

If the API returns some result, this will be provided as the second argument. You can also use create to define the model instance at the same time as you save it. The callback will return an error for the first argument and the newly-created model instance for the second argument. Every model has an associated connection this will be the default connection when you use mongoose. You can access the fields in this new record using the dot syntax, and change the values.

You can search for records using query methods, specifying the query conditions as a JSON document. The code fragment below shows how you might find all athletes in a database that play tennis, returning just the fields for athlete name and age. Here we just specify one matching field sport but you can add more criteria, specify regular expression criteria, or remove the conditions altogether to return all athletes. If you specify a callback, as shown above, the query will execute immediately.

The callback will be invoked when the search completes. Note: All callbacks in Mongoose use the pattern callback error, result. If an error occurs executing the query, the error parameter will contain an error document and result will be null. If the query is successful, the error parameter will be null, and the result will be populated with the results of the query.

If you don't specify a callback then the API will return a variable of type Query. You can use this query object to build up your query and then execute it with a callback later using the exec method. Above we've defined the query conditions in the find method.

Mongoose Find All

When working with databases, data retrieval is the most used operation of all the CRUD operations. When working with mongoose and MongoDB, documents of a collection can be retrieved using various methods. In this article, we will discuss such methods of retrieving documents from a collection in MongoDB. And we will use the postman tool for executing routes.

It then goes on to show how we can use Mongoose to provide database access for the LocalLibrary website. It explains how object schema and models are declared, the main field types, and basic validation. It also briefly shows a few of the main ways in which you can access model data.

In Mongoose , the Model. The first parameter to Model. MongoDB will search for all documents that match the filter. If you pass an empty filter, MongoDB will return all documents. In this tutorial, you'll see how to execute common queries in Mongoose by structuring the filter object using MongoDB query operators.

Express Tutorial Part 3: Using a Database (with Mongoose)

By using our site, you acknowledge that you have read and understand our Cookie Policy , Privacy Policy , and our Terms of Service. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Im having trouble using the. I'm mainly just having trouble wrapping my head around how this function takes queries and gives you back the response from your DB. If someone can break it down id be very thankful the mongoose docs weren't much help. As you can see, you're looking through the array for a key that matches the one you're looking to find and gives you back all of the documents that match that key search in the form of an array. The Mongoose interface gives this data to you in the form of a callback, and you just need to look for the item inside of the array it returns. Learn more. Asked 2 years, 3 months ago. Active 1 month ago.

Learn Mongoose find() by Example

Mongoose models provide several static helper functions for CRUD operations. Each of these functions returns a mongoose Query object. A mongoose query can be executed in one of two ways. First, if you pass in a callback function, Mongoose will execute the query asynchronously and pass the results to the callback. When executing a query with a callback function, you specify your query as a JSON document.

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How to Find Documents with Mongoose

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SEE VIDEO BY TOPIC: Populating Queries with Mongoose - Creating a REST API with abpentucole.com

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How find() Works in Mongoose

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Feb 26, - find(), find() is an instance method on the Query class. The Model. find() function returns an instance of Mongoose's Query class. The Query class represents a raw CRUD operation that you may send to MongoDB.

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