sequelize
Advanced tools
Sequelize is a promise-based Node.js ORM (Object-Relational Mapping) library for Postgres, MySQL, MariaDB, SQLite, and Microsoft SQL Server. It features solid transaction support, relations, eager and lazy loading, read replication and more. Sequelize follows the Active Record paradigm and allows developers to define models and their relationships in a way that abstracts database access, making it easier to maintain and evolve the application codebase.
Model Definition
This feature allows you to define models in Sequelize, which represent tables in the database. Each model can have various attributes and their respective data types.
const User = sequelize.define('user', { username: Sequelize.STRING, birthday: Sequelize.DATE });CRUD Operations
Sequelize provides methods for creating, reading, updating, and deleting records in the database, which correspond to the CRUD operations.
User.create({ username: 'alice', birthday: new Date(1986, 6, 20) }); User.findAll(); User.update({ username: 'alicejr' }, { where: { id: 1 } }); User.destroy({ where: { id: 1 } });Associations
This feature allows you to define associations between models. For example, a user can have many posts, and a post belongs to a user.
User.hasMany(Post); Post.belongsTo(User);Transactions
Sequelize supports transactions which allow you to execute multiple queries in an atomic way, ensuring data integrity.
sequelize.transaction(transaction => { return User.create({ username: 'bob' }, { transaction }); });Migrations
Sequelize has a migration tool that allows you to define changes to the database schema, which can be applied and rolled back programmatically.
module.exports = { up: (queryInterface, Sequelize) => { return queryInterface.createTable('users', { id: { allowNull: false, autoIncrement: true, primaryKey: true, type: Sequelize.INTEGER }, username: { type: Sequelize.STRING } }); }, down: (queryInterface, Sequelize) => { return queryInterface.dropTable('users'); } };Mongoose is an ODM (Object Data Modeling) library for MongoDB and Node.js. It manages relationships between data, provides schema validation, and is used to translate between objects in code and the representation of those objects in MongoDB. Compared to Sequelize, Mongoose is specific to MongoDB, whereas Sequelize supports multiple SQL databases.
TypeORM is an ORM that can run in Node.js and be used with TypeScript and JavaScript (ES5, ES6, ES7, ES8). It supports the Data Mapper pattern, unlike Sequelize which is more Active Record. TypeORM is highly influenced by other ORMs, such as Hibernate, Doctrine, and Entity Framework.
Knex.js is a SQL query builder for Postgres, MSSQL, MySQL, MariaDB, SQLite3, Oracle, and Amazon Redshift, designed to be flexible, portable, and fun to use. It does not provide full ORM capabilities but allows you to build and run SQL queries in a more programmatic and database-agnostic way. It is often used with objection.js, which is an ORM built on top of Knex.
Bookshelf.js is a JavaScript ORM for Node.js, built on the Knex SQL query builder. It features transaction support, eager/nested-eager relation loading, and polymorphic associations. Bookshelf follows a somewhat similar pattern to Sequelize but is built on top of Knex, which gives it a different flavor in terms of query building.
The Sequelize library provides easy access to MySQL, SQLite or PostgreSQL databases by mapping database entries to objects and vice versa. To put it in a nutshell... it's an ORM (Object-Relational-Mapper). The library is written entirely in JavaScript and can be used in the Node.JS environment.
up and down methods in migrations do have a third parameter which is the callback parameter. Pass an error or an error message as first parameter to the callback if something went wrong in the migration.You can find the documentation and announcements of updates on the project's website. If you want to know about latest development and releases, follow me on Twitter. Also make sure to take a look at the examples in the repository. The website will contain them soon, as well.
A very basic roadmap. Chances aren't too bad, that not mentioned things are implemented as well. Don't panic :)
I'm glad to get pull request if any functionality is missing or something is buggy. But please ... run the tests before you send me the pull request.
Still interested? Coolio! Here is how to get started:
Here comes a little surprise: You need Node.JS. In order to be a productive developer, I would recommend the latest v0.8. Also I usually recommend NVM.
Once Node.JS is installed on your computer, you will also have access to the lovely Node Package Manager (NPM).
First class citizen of Sequelize was MySQL. Over time, Sequelize began to become compatible to SQLite and PostgreSQL. In order to provide a fully featured pull request, you would most likely want to install of them. Give it a try, it's not that hard.
If you are too lazy or just don't know how to get this work, feel free to join the IRC channel (freenode@#sequelizejs).
For MySQL and PostgreSQL you'll need to create a DB called sequelize_test.
For MySQL this would look like this:
$ echo "CREATE DATABASE sequelize_test;" | mysql -uroot
CLEVER NOTE: your local MySQL install must be with username root
without password. If you want to customize that just hack in the
tests, but make sure to don't commit your credentials, we don't want
to expose your personal data in sequelize codebase ;)
AND ONE LAST THING: Once npm install worked for you (see below), you'll
get SQLite tests for free :)
Just "cd" into sequelize directory and run npm install, see an example below:
$ cd path/to/sequelize
$ npm install
Right now, the test base is split into the spec folder (which contains the
lovely BusterJS tests) and the spec-jasmine folder
(which contains the ugly and awkward node-jasmine based tests). A main goal
is to get rid of the jasmine tests!
As you might haven't installed all of the supported SQL dialects, here is how to run the test suites for your development environment:
$ # run all tests at once:
$ npm test
$ # run only the jasmine tests (for all dialects):
$ npm run test-jasmine
$ # run all of the buster specs (for all dialects):
$ npm run test-buster
$ # run the buster specs for mysql:
$ npm run test-buster-mysql
$ # run the buster specs for sqlite:
$ npm run test-buster-sqlite
$ # run the buster specs for postgresql:
$ npm run test-buster-postgres
Just commit and send pull requests.
Happy hacking and thank you for contributing.
Ah and one last thing: If you think you deserve it, feel free to add yourself to the
package.json. Also I always look for projects which are using sequelize. If you have
one of them, drop me a line!
As people are regularly complaining about missing semi-colons and strangely formatted things, I just want to explain the way I code JavaScript (including Sequelize ... obviously). I won't reject any pull-request because of having a different code style than me but it would be good to have a consistent way of coding in the whole project. Here are my rules of thumb:
var foo = function() {}Use spaces when defining functions.
function(arg1, arg2, arg3) {
return 1
}
Use spaces for if statements.
if (condition) {
// do something
} else {
// something else
}
var num = 1
, user = new User()
, date = new Date()
for (var key in obj) {
if (obj.hasOwnProperty(key)) {
console.log(obj[key])
}
}
{
"camelcase": true,
"curly": true,
"forin": true,
"indent": 2,
"unused": true,
"asi": true,
"evil": false,
"laxcomma": true
}
The automated tests we talk about just so much are running on Travis public CI, here is its status:
FAQs
Sequelize is a promise-based Node.js ORM tool for Postgres, MySQL, MariaDB, SQLite, Microsoft SQL Server, Amazon Redshift and Snowflake’s Data Cloud. It features solid transaction support, relations, eager and lazy loading, read replication and more.
We found that sequelize demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 8 open source maintainers collaborating on the project.
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