Primary key, column, sequence : best practice.

Question

Hi I was wondering when designing table should you limit the length of primary key.
Because if you have limited column length, and your adding and removing items than you have sequence gap, than you will need to resize column length and if their foreign key (resize them in foreign key relationship too) or you need to reset sequence to go back to the maximum (id).
WHat are the benefits and disbenefits of having limited column length. Is their way to restrict the maximum number of items without putting column length in their (inside the database) not the application.
Thanks.

Answer 1

Unless you know the exact number of rows your table will have, it is not convenient to limit the size. Now it all depend on what you mean by limiting the size and which column type you are talking about.
Here I have some notes about --> Why is Varchar2 oversizing bad?, where I state this:
Apparently the same space consumption would be the same if a Varchar2(4) is used versus a Varchar2(4000), if you require one byte, then one byte will be allocated, and performance should be the same, but when taking a look at the performance statistics there are some surprises that arise.
When fetching information from Oracle, buffers and fetching structures are being prepared beforehand to be able to manage the maximum column lenght, applications such as toad may run out of memory trying to allocate resources to retrieve the information from an unnecessarily over sized varchar2 column.
The answer to your case is: you should better plan according to your actual requirements, if you oversize columns you will degrade performance and you will have memory issues on the long run. If you under size then you will have problems with maximum capacity in your tables and you will be forced to -most probably- perform online maintenance to your objects to resize them.
~ Madrid
http://hrivera99.blogspot.com/