What does good database design require?

Answer 1

A well designed database will be normalized to the third normal form (3NF). The normal forms that are generally required to have a well designed database are First Normal Form (1NF), Second Normal Form (2NF), and Third Normal Form (3NF).

1NF states that each table has no dependency on top-to-bottom record ordering, left-to-right column ordering, no duplicate rows, and each column/row intersection contains exactly one value. For example, a column "Customer Name" is a bad idea; instead, consider "First Name" and "Last Name", since those are individual elements of a customer's full name.

2NF adds to 1NF by stating that each non-key column depends on the entire concatenated key (if the key is a composite primary key). For example, the description of an item would not belong in a table that stores items that were ordered; instead, it should be on the item table itself.

Finally, 3NF builds upon 2NF (and thus 1NF) by stating that data should not depend on a non-key attribute. For example, the customer's name should not appear in an order invoice table; the correct way to store this data would be in a customer table, with the order invoice table containing a reference to the customer table.

There are further forms (see any popular search engine for details), but those are generally considered more academic than practical in nature. In most cases, a database that fully conforms to 3NF will likely satisfy 4NF, 5NF, and 6NF, although there is no specific guarantee of that.

Answer 2

Ø Identify all the fields needed to produce the required information

Ø Organize each piece of data into its smallest useful part

Ø Group related fields into tables

Ø Determine each table's primary key

Ø Composite key

Ø Include a common field in related tables

Ø Avoid data redundancy

Ø Determine the properties of each field

Answer 3

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