Question

I have a problem that I can’t seem to solve.
I have table: Software
and table: PC

they both have many to many relationship between each other, that is, one PC can have many Software and One Software can have many PC’s
the link table is: soft-pc

The table soft-pc also has licensing information like, product keys.

now the problem is, when a software is deleted from a PC the record is deleted from the soft-pc table. Now I want to be able to un-associate software from PC and still have them in soft-pc table.

Is that possible?

Answer 1

Now I want to be able to un-associate software from PC and still have them in soft-pc table.

This is the core of the problem. At the moment, the relation predicate for the soft-pc table – that is, what it means for there to be a particular record in this table – is that the software in question is on the PC in question. If you now want to say that it’s possible for there to be a record in this table when there isn’t that software on that PC, you are going to have to decide what the new relation predicate is. Which is to say:

What does it mean for there to be a record in the soft-pc table?