请问一下,我查询了工序生产的日产量,想实现按查询内容的最后一行,减去第一行,请问这个思路是什么,代码怎么写;以下是我设计窗体查询内容的截图,和查询按钮的语句,敬请各位同仁指点一下,多谢;
```c#
//连接数据库
conn = new SqlConnection("server=IP;database=mes;user=sa;password=123");
conn.Open();
//查询条件
SqlString = "select EquipmentName,CreateTime,ParamsName,Value from b_HistoricalData where Equipmentname = '" + comboBox1.Text + "'and ParamsName like '%" + textBox1.Text + "%' and CreateTime >= '" + dateTimePicker1.Value.ToString("yyyy-MM-dd HH:mm:ss") + "' and CreateTime <= '"</span> + dateTimePicker2.Value.<span class="hljs-constructor">ToString(<span class="hljs-string">"yyyy-MM-dd HH:mm:ss"</span>)</span> + <span class="hljs-string">"' order by CreateTime asc";
//加载数据并显示
try
{
//查询条件和SqlConnection连接
SqlCommand cmd = new SqlCommand(SqlString, conn);
//数据适配器
SqlDataAdapter sda = new SqlDataAdapter();
sda.SelectCommand = cmd;
//DataTable存储数据
DataTable dt = new DataTable();
sda.Fill(dt);
dataGridView1.DataSource = dt;
}
catch
{ }
finally
{
conn.Close();
}
```