Adding Data to a Database Table

Carol WolfComputer Science

Adding data to a books table Create a books table using

rails generate scaffold book isbn:string author:string title:string

We can add data to the table using the New Book link at the bottom of the index page.

This is slow and for tables with a large number of fields very cumbersome.

Instead a lot of data can be added at once using either a migration or modifying seeds.rb in the db folder.

Using a migration Create a migration using

rails generate migration add_data This produces

class AddData < ActiveRecord::Migrationdef self.upend

 def self.downend

end Add data to get the following:

class AddData < ActiveRecord::Migration

def self.upBook.create(

:isbn => '4567-8901',:author => 'Chekov',:title => 'The Cherry Orchard')

Book.create( :isbn => ‘3412-4598’,:author => ‘Hemmingway’,:title => ‘The Sun Also Rises’)

…end

 def self.down

Book.delete_allend

end

Modifying seeds.rb seeds.rb is in the db folder. It is generated along with everything else when a

new rails project is created.# This file should contain all the record creation needed to seed the database with its

default values.# The data can then be loaded with the rake db:seed (or created alongside the db

with db:setup).## Examples:## cities = City.create([{ :name => 'Chicago' }, { :name => 'Copenhagen' }])# Mayor.create(:name => 'Daley', :city => cities.first) You can add data to it using the form indicated. It is run using rake db:seed. (Note: no plural)

# This file should contain all the record creation needed to seed the database with its default

values.# The data can then be loaded with the rake db:seed (or created alongside the db with

db:setup).## Examples:## cities = City.create([{ :name => 'Chicago' }, { :name => 'Copenhagen' }])# Mayor.create(:name => 'Daley', :city => cities.first) books = Book.create([ {:isbn => '4567-8901', :author => 'Chekov', :title => 'The Cherry Orchard'}, {:isbn => '3412-4598', :author => 'Hemmingway', :title => 'The Sun Also Rises'}, {:isbn => '1357-2468', :author => 'Steinbeck', :title => 'The Grapes of Wrath'}]) Note the curly braces around the hashes and the square

brackets around all the data. This is shorter than the migration and easier to do. But they

both work.