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daCypher
1 year ago

If it were SQL, it would be easy, but this is some wild mathematical formulation of relationships I’ve never seen in 15 years as a database admin. However, one can see it roughly as a series of primary key-refuse-key relationships, even if one cannot apply this to databases.

But to make it short: You can imagine the letters as columns in a table and the tuples are the values. The values from the columns that are left of the arrow clearly determine the value of the columns on the right side from the arrow. As I understood, you’re supposed to find out now that Tupel is no longer given the clarity.

I made a table so you can see what I mean:

In the yellow marked cells, there is a deviation where a key refers to different values. This means that in all values, except the tuple b) the relation is violated (at least if I have understood it correctly)

daCypher
1 year ago
Reply to  kali01

Because the values per key must always be clear. Once the table shows that the key 3 has the value 5, you cannot add a tuple where the key 3 suddenly has the value 4.

As I said, this is only very remotely applicable to SQL or to databases, but in databases one always tries to have as little redundancy as possible. Thus, for example, a customer should always be exactly under a customer number in the database, so that name or address changes are immediately applied correctly at all places.