What is meant by entity?: The entity integrity is a constraint on primary key value. It states that any attriburte of a primary key cannot contain null value. If primary key contains null value, it is not possible to uniguely identify a record in a relation.
Define referentioal integrity: The referentaila integrtiy is a constratint on foreign key value. It states that if a foreign key exitss in a relation, the foreign key value must match the primary key value of some tuple in its parent relation. Otherwise the foreign key value msut be completely null.
Hwo is entity integrtiy attained?
The intity integrity can be attained gby specitying primary key in a relation. When a primary key constrain is specified on a relation, the DBMS automtically applies the entity integrity on the attribute that is used as primary key.
Hw is referentiaol integrity achieved?
The referential integrity can be achieved by connecting two relations by specifying relationships between them. When two relations are connected, one relation is called parent relation and ;the other is called dependent relation.
A synonym is a type of problem that exists in relations. A synonym is created when two different names are used for the same information or attribute,. The name of attribute must be same if it exists in two or more entities.
A homonym is a type of problem that exists in relations. A homonym is created when same name is used for two different attributes.
Define the term redundancy.
Redundancy means duplication of data in multiple files. It is a type of problem that exists in relations it is created when the same information is unnecessarily stored in two different ways or forms.
Describe mutual exclusiveness of data.
The data that does not have overlapping information is known as mutually exclusive data. The mutual excursiveness of data creates problem in some cases it creates problem for the attributes whose values can be specified as “Yes/ No” form.
The process of producing a simpler and more reliable database structure is called normalization. It is used to create a suitable set of relations for storing data. It identifies and corrects the problems and complexities of database design, it produces a new set of relations. The new design is as free of processing problems as possible.
How is functional dependency associated with the process of normalization?
Normalization is performed as a series of tests on a relation to determine whether it satisfies or violates the requirements of a given normal form. All of these normal forms are based on the functional dependencies among the attributes of a relation.
Describe functional dependency with example.
A functional dependency is a relationship between attributes such that given the value of one attribute it is possible to determine the value of the other attribute. Example of functional dependency: Name–>Phone.
A determinant is an attribute whose value enables us to obtain the value (s) of other related attributes. It appears on the left side of a functional dependency. Thus, in A–>B, the determinant is A