ROR Q&A 1.1

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What is Migration & Its Advantage ?

Migrations are a convenient way for you to alter your database in a structured and organized manner.
Rails Migration allows you to use Ruby to define changes to your database schema.
Making it possible to use a version control system to keep things synchronized with the actual code.

Adv:-
Teams of developers : If one person makes a schema change, the other developers just need to update, and run "rake migrate".

Production servers   : Run "rake migrate" when you roll out a new release to bring the database up to date as well.

Multiple machines   : If you develop on both a desktop and a laptop, or in more than one location, migrations can help you keep them all synchronized.

List out what can Rails Migration do?
Rails Migration can do following things
  • Create table
  • Drop table
  • Rename table
  • Add column
  • Rename column
  • Change column
  • Remove column and so on


What are the different process and syntax of migration ?

$ rails g migration filename
only migration file will generate
$ rails g model modelname
Model file and migration file will generate

migration file change

1/Creating table name
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :firstname
t.timestamps null: true
end
end
end

2/ Add a Column to Table

class AddColumnToOrganisation < ActiveRecord::Migration
def change
add_column :table_name, :column_name, :data_type
end
end

3/ Rename column name of a Table
rename_column :table_name, :old_name, :new_name

4/ Change data type of a column

change_column :table_name, :column_name, :new_datatype

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