text: 
  exports.up = function (knex) {
    return knex.schema
      .alterTable('post', function (table) {
        table.renameColumn('author_id', 'user_id')
        table.integer('blog_id').unsigned().references('blog.id')
      })
  }
  
  exports.down = function (knex) {
    return knex.schema
      .alterTable('post', function (table) {
        table.renameColumn('user_id', 'author_id')
        table.dropColumn('blog_id')
      })
  }
  