Problems, Bad Database
Below you see a database with three tables.
This database has been badly designed.
Each table has a number of problems.
Problems of the table Subscription
- The publisher of the newspaper Computable is ambiguous (polyinterpretable).
For one reader it's Stam, for another one it's VNU.
- One and the same reader is registered with different spellings in the adminstration.
||Groenh. weg 43-II
Problems of the table Delivery Address
- The postcode 12345ABC is wrong, does not even match the Dutch format.
But there is no way to check the correctness of a postcode.
- The address of one reader is recorded twice.
That is not just cumbersome when the reader moves (dubble update), but it is unclear which one is the right version.
- The subscription of S Peuskens to Computable lacks address data.
||32 sep 1951
||Henk Jan Nootenboom
Problems of the table Invoice Data
- It's impossible to relate invoice data and subscriptions.
It's unclear which price is valid for a which newspaper.
Somebody can get an invoice bill, without subscription, or vice versa.
There isn't a good
- The postcode and city of Henk Jan Nootenboom are not existent in the Netherlands.
The invoice will never arrive.
It's impossible for the computer to get the address data from a different
table, as a result of a slightly different spelling of the name.
- Stefan Peuskens will get a invoice of 0 guilders, but will not receive a newspaper,
as the delivery address is unknown.
Could it be that this € 0,- has some special meaning and as a result there will be no invoice sent, and no newspaper delivered?
- The column birhtdate is irrelevant, is outside the scope.
The dates 01-04-1572 and 32 Sep 1951 are not reliable, probably specified wronly on purpose.