Long question, short answer: No.
There is nothing like an universal database on carbon footprints or similar. Of course there are a lot of websites which allow you to calculate the impact of - for example - travelling by plane or by car. But the actual calculation of such values is very complex and always comes along with a lot of research.
You mentioned the example of trains (Deutsche Bahn). Let's dig into it. What do we need to know for an objective estimation of your ecological impact?
- Model and size of train (ICE, IC, EC, RE, RB, S-Bahn, Tram, ...)
- Type of energy used (diesel, electricity, ...)
- Quantity of energy used
- Average speed, number of stops
- Number of passengers (occupancy)
With these accurate numbers you could calculate your ecological impact (carbon footprint) for traveling by train. I doubt that the Deutsche Bahn for instance is able to provide you with all these data. And even if they could, it's getting more complex. For example - if a train uses electricity - how do you know how the electricity was produced? It's a huge difference on the ecological impact if the train is powered by coal power plants or by renewable energy sources.
All you get is always some vague estimations. Let's have a look at flights. This is a very hot topic and a lot of sites on the internet offer some sort of calculators. Let's compare some.
One-way-flight Berlin (TXL) to Tel Aviv (TLV) - ca. 3,000km
The numbers above already tell you a lot about the "objective" nature of this issue.
Have a look at this one. This one allows you to adjust more parameters, for example type of plane and overall occupancy of the plane. Maybe a better resource. But still no full objective resource to estimate your travel impacts.
Well, I hope this is enough to answer your question and explained why I said "No" in the beginning. Calculating carbon footprints takes a lot of time for research or else you will only get very rough - sometimes unusable - estimates.