Question:What do you understand by one-to-one relationship between two tables? 

A relation between two tables such that one primary key value corresponds to one foreign key value is known as one-to-one relationship. In other words, each record in parent table is related to one and only one record in child table is one-to-one relationship.

Question:Clarify one-to-many relationship between two tables. 

A relation between two tables such that one primary key value corresponds to many foreign key value is known as one-to-many relationship. In other words, each record in parent table is related to zero or many records in child table is one-to-many relationship.

Question:Define many-to-many relationship. 

A relationship where many instances of an entity are associated with many instances of another entity is known as many-to-many relationship. Consider the enrollment relationship between a student and a class tables. A single student may be enrolled in many classes and a single class may enroll many students.

Question:What is identifying relationship? 

If the primary column is contributed to the child table's primary key or in other words, the foreign key is one of the columns in the child table's primary key, then this relationship is called an identifying relationship.

Question:What are the advantages of normalizing database design? 

The advantages of normalizing database are:
- Dependencies between data are identified.
- Redundant data and all of the problems associated with it is minimized
- The data model is flexible and easier to maintain.

Question:What are the E.F. Codd's normal forms? 

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.

Question:How is "no nulls" constraint implemented for an attribute? 

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.

Question:How is a "no changes" constraint implemented for an attribute? 

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.

Question:How is a "no duplicates" constraint implemented for an attribute? 

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.

Question:What is 'Required' property of a field? 

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