# Sequelize --- ## Sequelize is an ORM AN ORM (Object Relational Mapping) is a progrmaming technique that is used to convert data bewtween systems using objects. In our case we will be using an ORM to interact with the a databse and its tables. --- ## Why use one. Short Ans: Developers are LAZY!!! Long Answer: Developers are LAAAAAAAAAZY!!!! --- ## More Seriously ``` - SQL Commands are hard to write - Constantly wrting them will increase your chances of errors bc of its repetitive nature - Context switching. ``` --- ## What will we be learning - How to use SQLize CLI - How to use SQLize library --- ## Set up ``` npm i sequelize npm i --save-dev sequelize-cli ``` --- ## Initialize the Configuration ``` npx sequelize-cli init ``` --- ## Understanding the initialization ``` //directories - config: Edit database config - migrations: Keeps track of changes made in the database. These changes are done with migration commands - models: Schema. (Obejct that represents the databse table) - seeders: Contains the data that will be inserted into DB. ``` --- # SQLize Library Usage --- ## Set up ``` const { Sequelize, DataTypes } = require('sequelize') const sequelize = new Sequelize('xyz', '', '', { host: 'localhost', dialect: 'postgres' }); ``` --- ## Models Models are object representations of our database table. Sequelize will use this data to structure the table within out database. --- ## Define a model We define a model using the `.define()` method within the library. The first parameter is the name of the table you want. the second param is an object containing the columns and data types Note: The table name will automatically be pluralized upon creation. ex: User -> Users automatically ``` sequlize.define("Table_Name", { name: DataTypes.TEXT, age: DataTypes.INTEGER }); ``` --- ## Sync-ing models Syncing out models will allow us to create the database table. ``` const Table = sequlize.define("Table_Name", { name: DataTypes.TEXT, age: DataTypes.INTEGER }).sync() ``` *NOTE: you can also sync tables on connection* --- ## Sync-ing models on connection Syncing out models will allow us to create the database table. ``` try { await this.sequelize.sync({ force: true, logging: console.log }); console.log('Connection has been established successfully.'); } catch (error) { console.error('Unable to connect to the database:', error); } ``` --- ## Sequelize CRUD ``` .create() .findAll() .findByPk() .update() .destroy() ``` [CRUD Documentaion](https://sequelize.org/docs/v6/core-concepts/model-querying-basics/) ---