Relational databases
A relational A data store designed in an organised way, making it easier to search for the information you need. has more than one table and the tables are linked using A unique identifier for a database record or table entry.. For example, a library database could have three tables:
- Customer - when a customer joins the library a record is created. It stores their details such as their first name and surname and includes a unique Customer ID.
- Book - each book in the library has a record. It stores details about the book, such as the author and title and includes a unique book ID.
- Lending - when a customer borrows a book, the lending table stores the customer's unique ID and the book's unique ID in a record. The record could also include additional Data that has meaning, not just a number or a letter. such as when the book was borrowed and when it's due back.
The customer and book ID are both examples of key fields.
Advantages
- The book's details and the customer's details need only be entered into the database once.
- Because of this, mistakes are less likely to happen and if there were a mistake in a customer's record, for example, correcting it will correct the mistake database-wide.
- Duplication is avoided - this keeps the database's file size down.
- Details about books and customers are easily accessible using their unique IDs.
- Queries can be performed and reports generated, eg a list of books a customer has borrowed since joining the library.
