A good database is one that is simple to understand and well planned. The database doesn't have redundant tables. One can use ERD's (Entity-Relationship Diagrams) or EER's (Enhanced-Entity Relationship Diagrams) in order to make a good database.

Now about the scope; well if you have good database then

1. Easy to locate the data or information in no time.
2. No redundant data.
3. No repetition.
4. More security. Like if one is accessing or changing the data other can not change the same data at that time.
5. Table references (keys like : Primary and foreign keys) are easy to maintain.
   

And so on.