1) What is meant by functional dependency.
Functional dependency is the relationship between attributes such that the value of an attribute is determined by value of another attribute.
Example: Regno->Name (Functional Dependency)
That is, 'Name' is dependent on the attribute 'Regno'.
In this case, Regno is a primary key.
2) What is meant by transitive dependency.
Transitive dependency occurs when a non key attribute value is functionally dependent on another non key attribute.
Example: Empid->Jobtype
Jobtype->Hourpay
In this case, Jobtype is dependent on Empid.
In the second case, Hourpay is dependent on Jobtype, which is a non key attribute.
Therefore, when a non key attribute is dependent on another non key attribute, it is called as transitive dependency.
Note: In Database Management System, dependencies are not required. So we go for NORMALIZATION
to reduce dependencies.
3) The most desired level of normalization in DBMS is
3NF (3rd Normal Form)
Tip: For an effective DBMS, 3NF is most desirable and higher levels of
normalization is not advisable.'
3NF means you got to reduce Transitive dependencies.
4) What is the difference between primary key, composite keys.
Primary key: Primary key is used to uniquely identify each row of a table.
Tip: Primary key should be UNIQUE and NOT NULL.
Composite keys: If a table has more than one primary key in a table, then it is called as Composite keys.
5) What are anomalies. what are its types. How to solve them.
Anomalies are errors that generally occur due to bad database design.
There are three types of anomalies namely:
1. Insertion anomalies
2. Deletion anomalies
3. Update anomalies
We can solve anomalies by using normalization techniques.
6) What do you mean by a flat file database.
A flat file database is the one in which there are no programs.
It also does not possess cross file feature.
The main advantage of flat file database is that it provides management of User interfaces.
7) What are the types of data abstraction.
There are three types of data abstraction namely:
Physical level abstraction
Logical level abstraction
View level abstraction
Physical level abstraction: It is the lowest level of abstraction that describes How data are stored.
Logical level abstraction: The middle level of abstraction that shows What data are stored and what is the relationship that exists among the data.
View level: View level abstraction is the highest level of abstraction which shows only part of the entire database.
Shortcut trick: Physical level: How
Logical level: What
View level: Only part
8) What is data modeling.
Data modeling is the process of optimizing the way in which information is stored and used within an organization.
Data modeling provides a strong platform for development of systems design and system documentation.
9) What is denormalization in DBMS.
Denormalization is the reverse process of normalization.
Denormalization is the process of controlled introduction of redundancy(repetition) in the database.
The main aim of denormalization is to increase and improve query performance.
10) What is the difference between a tuple and an attribute.
A tuple denotes a row.
An attribute means a column.
Functional dependency is the relationship between attributes such that the value of an attribute is determined by value of another attribute.
Example: Regno->Name (Functional Dependency)
That is, 'Name' is dependent on the attribute 'Regno'.
In this case, Regno is a primary key.
2) What is meant by transitive dependency.
Transitive dependency occurs when a non key attribute value is functionally dependent on another non key attribute.
Example: Empid->Jobtype
Jobtype->Hourpay
In this case, Jobtype is dependent on Empid.
In the second case, Hourpay is dependent on Jobtype, which is a non key attribute.
Therefore, when a non key attribute is dependent on another non key attribute, it is called as transitive dependency.
Note: In Database Management System, dependencies are not required. So we go for NORMALIZATION
to reduce dependencies.
3) The most desired level of normalization in DBMS is
3NF (3rd Normal Form)
Tip: For an effective DBMS, 3NF is most desirable and higher levels of
normalization is not advisable.'
3NF means you got to reduce Transitive dependencies.
4) What is the difference between primary key, composite keys.
Primary key: Primary key is used to uniquely identify each row of a table.
Tip: Primary key should be UNIQUE and NOT NULL.
Composite keys: If a table has more than one primary key in a table, then it is called as Composite keys.
5) What are anomalies. what are its types. How to solve them.
Anomalies are errors that generally occur due to bad database design.
There are three types of anomalies namely:
1. Insertion anomalies
2. Deletion anomalies
3. Update anomalies
We can solve anomalies by using normalization techniques.
6) What do you mean by a flat file database.
A flat file database is the one in which there are no programs.
It also does not possess cross file feature.
The main advantage of flat file database is that it provides management of User interfaces.
7) What are the types of data abstraction.
There are three types of data abstraction namely:
Physical level abstraction
Logical level abstraction
View level abstraction
Physical level abstraction: It is the lowest level of abstraction that describes How data are stored.
Logical level abstraction: The middle level of abstraction that shows What data are stored and what is the relationship that exists among the data.
View level: View level abstraction is the highest level of abstraction which shows only part of the entire database.
Shortcut trick: Physical level: How
Logical level: What
View level: Only part
8) What is data modeling.
Data modeling is the process of optimizing the way in which information is stored and used within an organization.
Data modeling provides a strong platform for development of systems design and system documentation.
9) What is denormalization in DBMS.
Denormalization is the reverse process of normalization.
Denormalization is the process of controlled introduction of redundancy(repetition) in the database.
The main aim of denormalization is to increase and improve query performance.
10) What is the difference between a tuple and an attribute.
A tuple denotes a row.
An attribute means a column.
