CODEWITHSUNDEEP
ruby-on-railsdatabasemigrationdatabase-schema
Apprentice Programmer
Apprentice Programmer

Reputation: 1515

updating schema from a newly generated migration in rails?

How do i do this? My original schema I had a table called "users" that had a bunch of records. I deleted my original migration by accident and had to create a new one except the new one has a new additional record prior to the old one.

Sorry Im new to rails and databases specifically. Help would be greatly appreciated

Upvotes: 1

Views: 42

Answers (1)

franksort
franksort

Reputation: 3143

Maybe this will help you out.

Some Database Terminology

  • A database has schemas, tables, and records (upon other things).

  • A schema is the structure of the database. Things like table names, column names, and relationships.

  • A database has tables.

  • A table has records.

  • A record is a row of data in a table.

Migrations

A migration modifies the schema, or structure of the database, in some way. For example, creating a new table or adding a column to a table. Migrations are beneficial because you can keep track to the changes you make to the schema or even "undo" one.

An Example

Let's say we already have a users table but we want to add a column called 'full_name' to it. We can create a migration:

$ rails generate migration AddFullNameToUsers full_name:string

This will make a file in db/migrate called <date>_add_full_name_to_users.rb containing:

class AddFullNameToUsers < ActiveRecord::Migration
  def change
    add_column :users, :full_name, :string
  end
end

However, no changes have been made to the database yet! We need to execute the migration:

$ rake db:migrate

Now our users table has a new column called full_name. If we want to undo that we can rollback the migration:

$ rake db:rollback

Our user table no longer has a full_name column.

Upvotes: 1

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