rails db migrate code example

Example 1: how create migration rails

rails g migration AddPartNumberToProducts

Example 2: rails g migration add columns

$ rails generate migration AddDetailsToProducts part_number:string price:decimal

Example 3: activerecord add column

class AddPartNumberToProducts < ActiveRecord::Migration[6.0]
  def change
    add_column :products, :part_number, :string
  end
end

Example 4: ruby on rails db migrate

rails db:migrate

Example 5: rials db down

bin/rails db:migrate:down VERSION=YYYYMMDDHHMMSS

Example 6: how to create an SQL table in ruby

def self.create_table
    sql = <<-SQL
      CREATE TABLE IF NOT EXISTS students (
        name TEXT,
        grade TEXT
      )
    SQL
    DB[:conn].execute(sql)
  end