Hmm even my question isn't clear yet:

So, if I have database of photos of animals, plants and there can be 0,1 or more of same species, For instance bear. To throw away languaga troubles the key could be latin, for bear --> Ursus ..something.

The key is string, is this good ?
When user, that is me, admin only, ads new photo, and don't remembeer that there is already Ursus in database, further more mistype something ...ahh --> gets 2 recorda that should be one ....

Code:
master -->  key1
detail   --> key1 --> Ursus image 1
detail   --> key1 --> Ursus image 2
any thoughts ?