code: public OqlBuilder<T> groupBy(final String what) {
      if (Strings.isNotEmpty(what)) {
        groups.add(what);
      }
      return this;
    }
docs: groupBy.
  
  @param what a {@link java.lang.String} object.
  @return a {@link org.beangle.commons.dao.query.builder.OqlBuilder} object.