connect my migrate table with controller to get data in ruby on rails code example

Example 1: change column rails example

def change
    change_column(:table_name, :column_name, :new_type)
end

Example 2: activerecord add column

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

Example 3: 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