select * from test 
  where 洪水量 in (select max(洪水量) from test)

------解决方案--------------------

SQL code
 --查询每天的洪水最大量   
 select convert(varchar(10), tiTime,20) as 'DailyDate',MAX(洪水量)    
      from tb 
        group by convert(varchar(10), tiTime,20)

------解决方案--------------------
select top (1) * from test order by 供水量 desc

------解决方案--------------------
如果最大供水量有相同的多个，请执行如下代码：
select top (1) with ties * from test order by 供水量 desc