Database Environment In Management Systems Short Interview And Test Questions
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Q.1. What is three-level architecture?
Three-level architecture is the basis of modern database architecture. The database can be viewed at three levels. The three levels are depicted by three models known as three-level schema. The purpose of the three-level architecture is to separate the way the database is physically represented from the way the user thinks about it.
Q.2. Name and explain the purpose of three schemas in the ANSI/SPARC three schema model.
External Schema: The external schema or user view is a representation of how users view the
database. An external schema portrays just a portion of the database.
Conceptual Schema: A conceptual schema is a complete logical view of a database that contains a
description of all data and relationships in the database. The conceptual schema is logical. It is independent
of any particular means of storing data.
Internal Schema: An internal schema is a representation of a conceptual schema as physically stored using a particular product and/or technique. The description of a set of tables, keys, foreign keys, indexes, and other physical structures is an internal schema.
Q.3. How are external schemas used to devise one conceptual schema?
External schemas are descriptions of the world as end-users see the world. During the database design process, designers collect information from end-users and develop different external schemas for different end-users. These external schemas are then combined into one conceptual schema.
Q.4. What is a hierarchical database? Write down the advantages and disadvantages of the Hierarchical database model.
Hierarchical databases organize data in a series like a family tree or organizational chart. The hierarchical database has branches made up of parent and child records. Each parent record can have multiple child records but a child record can have only one parent.
Advantages
1. Hierarchical DBMS is good for one-to-many relationships.
2. It can store large numbers of segments and process information efficiently.
3. It is a simple structure and minimizes disk input and output.
Disadvantages
1. It is less user-friendly.
2. It creates inflexibility and programming complexity.
3. It is difficult to reorganize the database as a hierarchy has to be maintained.
Q.5. What is a data model? List main types of data models.
A collection of concepts to describe and manipulate data, relationships between data, and constraints on data is called a data model. Object-based data models such as the Entity-Relationship model. Record-based data models such as the relational data model, network data model, and hierarchical data model. Physical data models describe how data is stored in the computer.
Q.6. What is a relational database? List its advantages and disadvantages.
Relation database organizes data in two-dimensional tables called relations. Each row in a table is called a tuple and each column is called an attribute. A tuple is also called a record or row. The range of values that an attribute can have is called domain.
Advantages
1. It has the capacity to link multiple files together.
2. It provides the facility of data independence.
3. It provides the facility of structural independence.
4. It provides the facility of data integrity.
5. It has the capability to add new fields.
6. It provides the facility to establish relationships at any time.
Disadvantages
1. It is a bit poor in processing efficiency.
2. Response time can be very slow its large numbers of accesses to data are required to select, join, and extract data from tables.
Q.7. Describe the role and responsibilities of a database administrator (DBA).
1. The development and management of the organization's databases.
2. He must work with a number of people including systems analysts, programmers, users, managers, and security personnel.
3. He assists in the design and implementation of the database.
4. He helps to establish policies and procedures
5. He assists to ensure the security of the database.
Q.8. What is the difference between Data Administrator and Database Administrator?
The data administrator is responsible for corporate data resources. It includes non-computerized data. He manages shared data of users or application areas of an organization. He determines long-term goals and enforces stan policies and procedures. He also determines data requirements and develops conceptual and logical designs. His work is DBMS-independent. The database administrator is more technically oriented. He requires the knowledge of a DBMS. He develops and maintains systems using DBMS. He executes plans to achieve goals. He enforces standards, policies, and procedures developed by DA. He develops logical and physical design. His work is DBMS-dependent.
Q.9. What is a data dictionary?
The data dictionary is a repository of information that describes the logical structure of the database. It contains record types, data item types, and data aggregates, etc. The data dictionaries in some systems store database schema and can be used to create and process the database. The data dictionary contains metadata. Metadata is the data about the data stored in the database.
Q.10. List some uses of the data dictionaries.
1. It is used to collect and store information about data in a central location.
2. It provides great help in communication as it stores the exact meanings of data items.
3. It keeps track of changes to the database structure.
4. It records each item, its relationships, and its users. DBA can see the effects of a change.
5. It stores all information about different authorized users.
6. It can also keep a record of each access to the database to be used for audit purposes.
Q.11. Describe different types of data dictionaries.
Different types of data dictionaries are as follows:
1. Integrated Data Dictionary: A data dictionary that is part of DBMS is called an integrated data dictionary. They perform many functions throughout the life of the database not only in the design phase.
2. Freestanding Data Dictionary: A data dictionary that is available without a particular DBMS,
is called a freestanding data dictionary. It can be a commercial product or a simple file developed by
the designer. Many CASE packages provide a data dictionary tool. It is preferable in the initial design
stages before choosing any particular DBMS.
Q.12. Differentiate between active and passive data dictionaries.
The integrated data dictionary is called active if it is checked by DBMS every time a database is
accessed. It is always consistent with the actual database structure. It is automatically maintained by the
system. The integrated data dictionary is called passive if it is not used in day-to-day database
processing
Q.13. What are the effective measures of database design?
The major effectiveness measures of database design are as follows:
a. Ensuring that data can be shared among users for a variety of applications.
b. Maintaining data that are both accurate and consistent.
c. Ensuring all data required for current and future applications will be readily available.
d. Allowing the database to evolve and the needs of the user to grow.
e. Allowing users to construct a personal view of data without concerning the way it is physically
stored.
Q.14. What elements of a data flow diagram should be analyzed as part of data modeling?
Datastores, data flows, and even processes provide information for data modeling. A data store
often represents one or more data entities and their associated attributes. All data in data flows must
either be stored in some entity, be computed from data in entities, or pass through the system. The
description of a process can indicate business rules that must be represented in the data model
