Question

In a library database, where would you have the potential for repeating groups? What are the potential problems? Explain.

Answer 1

Repeating groups as the name suggests is let's say the category of information which has been redundant in the database in multiple tables.

Let's take the case of a library database

Here let's say we have a table for books and the subjects it has, author, book I'd, book cost etc but now we have another table for top rated books or let's say reserved books

There we have the same details like book ID, author and the book cost, reserved by, department, copies now the data are different but we have Redundancy in the data as the name of author, price and book are repeating here.

This is called repeating groups

possible problems-

Let's say that the inflation increased the cost of the book and we updated that in the book in the table but forgot to mention the same change in the reserved table.

So how would you maintain the data consistency, similarly if I say get me the reserved book, it's location and publications ( from book list table) whose cost is above some value

Now the data in first table is let's say 300 and new price is 400 and my value is 359 so I'll get a messed up situation where I can see that the data is 350 in one table but it is passing 359+ as its value in another table is 400.