Compare date from datetimepicker with date from database

//How can i do to when i select one date < or = (select u_replica from e_industrial.dbo.e1) from this query, if true show date, if > dont show.


 private void btn_search_Click(object sender, EventArgs e)
        {
            
            SqlConnection conn = new SqlConnection("Data Source=....;Initial Catalog=Innux;Persist Security Info=True;");
            conn.Open();
            SqlDataAdapter SDA = new SqlDataAdapter("select dbo.Alteracoes.Data, dbo.Funcionarios.numero as no, dbo.Funcionarios.nome, DATEPART(hour, Falta) AS faltas, DATEPART(hour, Coluna2) AS  horasextra  from dbo.Alteracoes inner join dbo.Funcionarios on dbo.Alteracoes.IDFuncionario = dbo.Funcionarios.IDFuncionario inner join dbo.Departamentos on dbo.Funcionarios.IDDepartamento = dbo.Departamentos.IDDepartamento WHERE Data = '" + dateTimePicker1.Value.ToString("yyyy/MM/dd") + "'", conn);
            DataSet dt = new DataSet();
            



            SDA.Fill(dt, "dbo.Alteracoes.Data");
            dataGridView1.DataSource = dt.Tables["dbo.Alteracoes.Data"];
            conn.Close();
        }

        private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
        {

            //dateTimePicker1.MaxDate = DateTime.Now;
            SqlConnection conn = new SqlConnection("Data Source=.....;Initial Catalog=Innux;Persist Security Info=True;");
            conn.Open();
            SqlDataAdapter pickerMaxDate = new SqlDataAdapter("select u_replica from e_industrial.dbo.e1 ('"+  dateTimePicker1.Value.ToString("yyyy/MM/dd")+"')" , conn);

            String pickerMaxDateString = pickerMaxDate.ToString();
            DateTime dtMax = Convert.ToDateTime(pickerMaxDateString);

            dateTimePicker1.MaxDate = dtMax;

            
            conn.Close();
        }

private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
      {

          //dateTimePicker1.MaxDate = DateTime.Now;
          SqlConnection conn = new SqlConnection("Data Source=.....;Initial Catalog=Innux;Persist Security Info=True;");
          conn.Open();
          SqlDataAdapter pickerMaxDate = new SqlDataAdapter("select u_replica from e_industrial.dbo.e1 ('"+  dateTimePicker1.Value.ToString("yyyy/MM/dd")+"')" , conn);

          String pickerMaxDateString = pickerMaxDate.ToString();
          DateTime dtMax = Convert.ToDateTime(pickerMaxDateString);

          dateTimePicker1.MaxDate = dtMax;


          conn.Close();
      }