Microsoft Access Database

Is used to describe a data in a detailed way. It contains all entities and relationships among them, specify all attributes for each entity and specify both primary and foreign keys for each entity.

It is where normalization of data is done and help to analyses database.

Key

· Solid red underline is for primary keys

· Dotted blue underline is for foreign keys

First Normal Form (1NF) - Is where a group of information can’t be allowed to repeat itself in two or more rows in a table. Each row must have a unique value. Primary is placed on one column but at times can have many columns. For example:-

And thus its INF for the above table will be:-

Any row must not have a column with more than one value for example separated by a comma. Then you must separate that data and put them in multiple rows.

This help to increase data redundancy because many columns with same data in multiple rows are created but each row will be unique.

Second Normal Form (2NF)

If is in INF and all of its non-key attributes are fully functional dependent on the primary key.

For example:-

2NF for the above will be:-

From the 2NF tables above, Order_total_price is fully dependent on the primary key Item_id.

Third Normal Form (3NF) is where a table must be in 2NF and for every non-prime attribute should be dependent on the primary key.

For example:-

3NF for the above will be:-

Customer_zip is a transitive dependency but Customer_id is the primary key for the above tables. To apply 3NF Customer_zip becomes the new primary key because it is depended by the address, city and state of a customer and a new table is created for such.

The importance of removing transitive dependency is that data duplication is reduced in a table and data integrity is attained.