Web Forms :: Difference Between Return Value Of ExecuteNonQuery And ExecuteScalar

I use below code for my button event

int Result = _cmd.ExecuteNonQuery();
if (Result > 0)
{
Session["Login"] = true;
Response.Redirect("~/Managers.aspx?BehCode=" + Server.UrlEncode(TextBox1.Text));
}

But it didn't work it didn't go to managers.aspx page but when I replace code with below code it worked correctly it go to managers.aspx

int count = Convert.ToInt32(_cmd.ExecuteScalar());
if (count > 0)
{
Session["Login"] = true;
Response.Redirect("Managers.aspx?BehCode=" + Server.UrlEncode(Txtbeh.Text));
}

Why this happen whats exact different between two code?