code: public String[] getColumnsBySql(Sql sql) throws SQLException {
  		String columns[] = null;
  		
  		List<Map<String, String>> table = getMetadataBySql(sql);
  		if (table != null) {
  			columns = new String[table.size()];
  			for (int i = 0 ; i < table.size() ; i++) {
  				Map<String, String> row = table.get(i);
  				if (row.containsKey("NAME") && row.get("NAME") != null) {
  					columns[i] = row.get("NAME");
  				}
  			}
  		}
  		
  		return columns;
  	}
docs: 根据SQL语句获取SQL返回的列名
  
  @param sql SQL语句
  
  @return 列名
  
  @throws SQLException SQL执行异常