Hi all , i'll show you my problem.
Here are the table:
Now , Library_holding is a number that tells how many libraries have that book.
I want to make a query between these two tables that has this structure
Average for a book should be the division of how many libraries hold that book compared to all libraries.
If in the database i have 20 libraries memorized and Book1 is present in 3 libraries average should be 3/20. How can i do this? Thanks in advance