After burning the midnight oli searching for an answer my question goes out to you and is about keyword hierarchy. Pretty straitforward:
A) If I add a keyword to a picture which belongs to a parent keyword - is then this parent keyword also always linked to the picture?
As far as I know, YES.
B) And if so: Is there a way to avoid that?
If you don't want to find the parent keyword, then don't make the keywords hierarchical
Why is that important?
I grouped my keywords so that I apply some sort of system when I keyword. One category for example is PEOPLE which contains the keywords FAMILY, FRIENDS and NO PEOPLE (for pictures which include no people and the case that I look for an empty street or a lone path). If I now link the keyword "NO PEOPLE" to a picture than this picture will also show up when I am searching for only for the parent keyword "PEOPLE" which in the end dose not make sense because there are no people in this image.
There is no logical reason to make NO PEOPLE a child keyword of the parent keyword PEOPLE. Change this, and your problem goes away.
Thanks for your help
Talking about question B: I would like decidedly to finde it in there
Talking about logic: I think the example above entitles the hierarchy
You can have your own logic, but if it conflicts with the way Lightroom works, you can't then achieve what you want. Lightroom won't change the way it works because you use different logic.
So, again I say, if you remove NO PEOPLE from the PEOPLE hierarchy, you now can find the desired photos. The point of a keyword list and hierarchy, after all, is to enable you to find the desired photos. The point is not to have a specific keyword list and hierarchy that doesn't help you find the desired photos.
dj_paige's suggestion seems the simplest solution that's compatible with LR's capabilities. Instead of:
If you really want to maintain your current hierarchy, then you could search for all People child keywords except for No People by using the Library Filter bar (Library Enable Filters):
As with most lists, you can click on the first keyword and shift-click on the last one to select all of the keywords in between.
But you'd still have problems with the other keyword search features of LR: Clicking on the arrow to the right of People in the Keyword List pane, doing a Library Filter Text search of Keywords, searching keywords with smart collections. That's why dj_paige's suggestion is simpler.