C sharp - ExecuteNonQuery problemas

conex.Open();

string sql = "INSERT INTO T14Tiempos (IDCarreraT14, IDTramoT14, IDParticipanteT14,TSalidaT14)" +

	"VALUES ('" + valores[0] + "', '" + valores[1] + "', '" + valores[2] + "', '" + valores[3] + "')" +

	"ON DUPLICATE KEY UPDATE TSalidaT14 = IF(NULLIF(TSalidaT14, ' ') IS NULL, '" + valores[3] + "', TSalidaT14);";

MySqlCommand sql_ins = new MySqlCommand(sql, conex);

int i = sql_ins.ExecuteNonQuery();

if (i == 1)

{

	MessageBox.Show("Tiempo insertado / actualizado!");

}

else

{

	MessageBox.Show("Tiempo asignado anteriormente");

}

conex.Close();