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