text: 
  exports.up = function(knex) {
      return knex.schema
      .createTable('classes', (tbl) =>{
          tbl.increments('id');        
          tbl.string('class_name', 128).notNullable();
          tbl.string('class_type', 128).notNullable()
          tbl.string('intensity_level', 128).notNullable();
          tbl.string('duration', 128).notNullable();
          tbl.string('start_time', 128).notNullable();
          tbl.string('location', 128).notNullable();
          tbl.integer('number_of_attendees');
          tbl.integer('max_class_size');
      })
      .createTable('users', (tbl) =>{
          tbl.increments();
          tbl.string('username', 128).unique().notNullable();
          tbl.string('password', 128).notNullable();
          tbl.string('role').notNullable();
          tbl.integer('class_id').references('id').inTable('classes');
      })
  };
  
  exports.down = function(knex) {
      return knex.schema
      .dropTableIfExists('users')
      .dropTableIfExists('classes')
  };
  