Migrations

Migrations are a convenient way for you to alter your database in a structured and organised manner. You could edit fragments of SQL by hand but you would then be responsible for telling other developers that they need to go and run it. Adds a new foreign key. Fromtable is the table with the key column, totable contains the referenced primary key. The foreign key will be named after the following pattern: fkrails.identifier is a 10 character long string which is deterministically generated from the fromtable and column.A custom name can be specified with the:name option. In the first command rails generate model Micropost userid:integer it only adds a column userid however rails does not know the use of the col. The keywords belongsto and hasmany determine the relationship between these models and declare userid as a foreign key to User model. Oct 23, 2009  In this article, we learned how to design and create tables for a User Management Module in Ruby on Rails. We looked at designing the E-R model, deriving the schema from the E-R model and creating the tables from the schema.

Migrations are a convenient way for you to alter your database in a structuredand organized manner. You could edit fragments of SQL by hand but you would thenbe responsible for telling other developers that they need to go and run them.You’d also have to keep track of which changes need to be run against theproduction machines next time you deploy.

Ruby on rails generate model with foreign key youtube

Ruby On Rails Generate Model With Foreign Key Code

Rails

Active Record tracks which migrations have already been run so all you have todo is update your source and run rake db:migrate. Active Record will work outwhich migrations should be run. It will also update your db/schema.rb file tomatch the structure of your database.

Migrations also allow you to describe these transformations using Ruby. Thegreat thing about this is that (like most of Active Record’s functionality) itis database independent: you don’t need to worry about the precise syntax ofCREATE TABLE any more than you worry about variations on SELECT * (you candrop down to raw SQL for database specific features). For example you could useSQLite3 in development, but MySQL in production.

In this guide, you’ll learn all about migrations including:

  • The generators you can use to create them
  • The methods Active Record provides to manipulate your database
  • The Rake tasks that manipulate them
  • How they relate to schema.rb

Chapters

  1. Anatomy of a Migration
  2. Creating a Migration
  3. Writing a Migration
  4. Running Migrations
  5. Schema Dumping and You
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