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Wednesday, 6 April 2016

ICS Notes Computer Science Part 2 Chapter 2 Basic Concepts and Terminology Short Questions

ICS Notes Computer Science Part 2 Chapter 2 Basic Concepts and Terminology Short Questions

Q 1. Define relation.
Ans. In relational database the table in which data is stored is called a relation. Collection of rows and column is called table. Each intersection of a row and column is called cell. Table contains the descriptive information about an entity. Table is also called relation. Each file in a file management system corresponds to a table in database management system.

Q 2. What is an Entity?
Ans. Anything about which we want to store data is called entity. It can be a person, place or event etc. Entity always has a unique name with in a domain.

Q 3. What is the use of views?
Ans. Views are virtual table used to keep data safe and secure from unauthorized access. Unlike ordinary table in a relational database, a view is not a part of physical schema. It is dynamic, virtual table computed from data in the database. Changing the data in a table alters the data shown in view.

Q 4. What is a key?
Ans. A key field is a field or set of fields of a database table which together form a unique identifier for a database record. The aggregate of these fields is usually referred to simply as "the key". A key field also defines searches.

Q 5. Define primary key.
Ans. In a relation the attribute or a combination of attributes that uniquely identifies a row or a record. e.g. A social security number, ISBN, student roll number, etc.

Q 6. Define secondary key.
Ans. A secondary key is a non-unique field that is used as a secondary or alternate key. Some times records are required to be accessed by a field other than the primary key. In these situations another key that is used is called secondary key or alternate key.

Q 7. Define candidate key.
Ans. There can be more than one keys or key combinations that qualify to be selected as primary key. In a relation there can be only one primary key at a time. Rest of the keys or key combinations are called candidate keys.

Q 8. Define composite key.
Ans. Composite key consists of two or more than two fields. Composite key is also designated as a primary key. It is created in a situation when no single field fulfills the property of uniqueness. To make unique more than one field are combined and used as primary key.

Q 9. Define sort key.
Ans. A field or a set of fields in a record that dictates the sequence of the file according to our requirement. For example the sort keys STATE and NAME arrange the table data alphabetically by name within state. STATE is the major sort key, and NAME is the minor sort key.

Q 10. What is the use of index file?
Ans. Indexes are stored in index file. DBMS uses index files to speed up the sorting and searching operations.

Q 11. Who is end user?
Ans. It is the person who uses the database management system for his need. He must have knowledge of information technology. He does not need to have the detail knowledge of the computer system. He should be aware of the usage details of the software he intends to use.

Q 12. Who is data administrator?
Ans. The DA department is responsible for the definition, organization, supervision and protection of data in order to provide good quality, shareable and accessible data throughout the enterprise. The Data Administrator manages a staff that is responsible for establishing and implementing the Data Administration Program.

Q 13. Who is database administrator?
Ans. A database administrator (DBA) is a person who is responsible for the environmental aspects of a database. In general, these include:
  • Recoverability: Creating and testing backups.
  • Integrity: Verifying or helping to verify data integrity.
  • Security: Defining and/or implementing access controls to the data.
  • Availability: Ensuring maximum up time.
  • Performance: Ensuring maximum performance given budgetary constraints.
  • Development and testing support: Helping programmers and engineers to efficiently utilize the database.

Q 14. List two properties of a relation.
Ans. Properties of a relation.
  • It has unique column names.
  • The order of column is insignificant.
  • The order of row is insignificant.

Q 15. Discuss the data manipulation in DBMS system?
Ans. Data manipulation of database management system is different from file management system. In database management system.
  • Data is stored in relation or tables.
  • A database may have more than one relation with unique names.
  • Relations in a database relate to each other using primary and foreign keys.
  • DBMS uses index to quickly access the data stored in relation.
  • Database query language i.e. SQL is used for data manipulation in database. 

Written by: Asad Hussain

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