code: function executeQuery () {
      return this.model.mysql().query(this.select.sql, this.select.params)
      // decode data
      .then(results => {
          // decode any encoded data columns
          return this.decodeData(results)
      })
      // add custom error handler
      .catch(err => {
          throw this.error('db error', err)
      })
  }
docs: @function executeQuery
  
  execute query
  
  @returns {Promise}