note On Nov.21 about SQL Query

 

为DATATABLE添加行

DataRow row;
            while (dt.Rows.Count < 10)
            {
                row = dt.NewRow();
                row[0] = null;
                row[1] = DBNull.Value;
                dt.Rows.Add(row);
            }

遍历DATATABLE

for (int i = 0; i < dt.Rows.Count; i++)
        {
            for (int j = 0; j < dt.Columns.Count; j++)
            {
           
                Response.Write(dt.Rows [i][j]);

               
            }
        }

查询所有传感器最近时间的信息

  select topotest.*
from (select source,MAX(time) as time from topotest group by source)
temp inner join topotest on
temp.source = topotest.source and temp.time = topotest.time