As far as I know from my book, keys are categorized into "Perfect/ Primary/ Key" and
=> "Primary key" means that the key is unique, but the "Subset ratio" is less than 100%.
Now, I guess that translates to "Anteil der Werte" (the third value from the top displayed in that hover_over_window)
<=> Why do I, in one table I have just integrated into my data_model, a key with the quality "Key", but with a "subset ratio" of 100%? (The other value is also 100% in case that makes a difference)
Thanks a lot if anyone can clarify this!
P.S.: The background is - there is an older version of this app where I have joined this table with another - but now I'm not sure about this: Joining with a non-unique key does not seem to be a good idea.