Following are the Codd's normal forms:
- First Normal Form: Eliminate repeating groups of attributes in an entity.
- Second Normal Form: Eliminate partial key dependencies, i.e. each attribute in an entity must depend on the whole key, not just a part of it.
- Third Normal Form: Eliminate redundant information by eliminating interdepencies between non-key attributes.

The not null (NN) concept allows the database desi gner to force the user to enter a value in a particular column. The not null concept is used for columns involved in a primary key. The option must be set when table is created, and set by using the NULL or NOT NULL keywords.

The no change (NC) concept allows the database designer to prohibit changes to the values in a column. This concept is used mainly for columns participating in primary keys. Preventing changes to a primary key is recommended because primary keys are used to create relationship between tables, and changes to a primary key could result in a referential integrity violation.

The no duplicate (ND) concept specifies that the values in a column must be unique. This concept is used in primary keys and alternate keys.

Required property specifies if data must be entered in a field or not. If set to Yes, user can't leave the field blank.