Duplications?

[Tansar]

Hello,

I am trying to create a Library DB, and noticed that we have more than 1 copy of the same book. I have set the ISBN number as the primary key - so I think that I may need to change it (?)

The advise that I am seeking is how do I go about showing that the library has 3 copies but only 2 are available as 1 is on loan. Any advice much appreciated.

TIA

 

[Rich]

Search here for Loan, there have been many posts on the subject

 

[Tansar]

I've done the search but found things relating to loans of a different kind. I've also tried library and got weird answers.

Is ther anyone who is willing to help?

TIA

 

[dcx693]

Here are some tips to point you in the right direction.

You're right about ISBN by itself not being sufficient as a primary key field since multiple books can have the same ISBN number. You need to add something additional to it, like the edition or revision number, or a simple arbitrary copy number to differentiate between multiples. Say you decide to throw in the copy number. With that and the ISBN, you can create a compound primary key, using the two fields together to unique identify each book.

Your database should have a loaned out date to tell you when the book was loaned out. You should also have a returned date. The usual logic would be, if the loan date is filled in but the returned date is empty then the book is out.

 

[Tansar]

Thank you for your well explained answer. I'll give that a try.

 

[Tansar]

Is there a sample of the 'video store model' anywhere?