code: func (q *Query) Exists() (bool, error) {
  	cp := q.Copy() // copy to not change original query
  	cp.columns = []QueryAppender{Q("1")}
  	cp.order = nil
  	cp.limit = 1
  	res, err := q.db.ExecContext(q.ctx, newSelectQuery(cp))
  	if err != nil {
  		return false, err
  	}
  	return res.RowsAffected() > 0, nil
  }
docs: // Exists returns true or false depending if there are any rows matching the query.