求解释下面这段代码 。。。Rows.Count > 0)这个什么意思，。在线等

if (this.txtUserID.Text == "")
{
lblMessage.Text = "请输入用户名！";
return;
}

switch (this.RadioButtonList1.SelectedValue)
{
case "员工":
if (DataControl.GetData("select * from 员工 where 员工编号='" + txtUserID.Text + "' and 密码='" + txtPwd.Text + "' and 职位 = '主任'").Rows.Count > 0)
{

Session["User"] = txtUserID.Text;
Response.Redirect("ZR/index.aspx");
}
else if (DataControl.GetData("select * from 员工 where 员工编号='" + txtUserID.Text + "' and 密码='" + txtPwd.Text + "' and 职位 = '员工'").Rows.Count > 0)
{

Session["User"] = txtUserID.Text;
Response.Redirect("YG/index.aspx");
}
else
{
Page.RegisterClientScriptBlock("onload", "<script>alert('密码错误');</script>");
return;
}
break;
case "管理员":
if (DataControl.GetData("select * from 管理员 where 帐号='" + txtUserID.Text + "' and 密码='" + txtPwd.Text + "' ").Rows.Count > 0)
{
Session["User"] = txtUserID.Text;
Response.Redirect("Admin/index.aspx");
}
else
{
Page.RegisterClientScriptBlock("onload", "<script>alert('密码错误!');</script>");
return;
}
break;
}

查询到的结果的条数是否大于零，换个意思就是说有查出东西没