12th Class Chapter 2 Computer science Short Questions

Write down the basic purpose of using views.

Views are created by using SQL,which is powerful database language,used for data manipulation purpose.The purpose of using views is purely to keep the data safe and secure from unauthorized and illegal users.The view provide the description of relation that are not stored ,but constructed as needed from stored relations.

Enlist four properties of a relation.

A table or relation or table which is basis of relational DBMS,by definition must have certain inherent characteristics that form the basis for its underlying strength and flexibility.These characteristics are:

What is the Key?

A key is a single or combination of one or more fields and its purpose to point/retrieve the data rows from the tables,according to the requirements.Keys are defined in the relation/tables to access or sequence the stored data fast and smooth or to create the links between them.

Define Indexes.

Indexes is a table created by the system developer/DBA containing the key attributes of the table for which the index is created .It has a very vital role in the database management system,especially in RDBMS,The important association defined in the system make use of this.It helps the system run smoth and fast.

Define the term Table or Relation.

Table or Relation is a two dimensional array or table of data containing descriptive information about entity.The entity must have a unique identifier,which is composed of an combination of one or more attributes,and each attributes must have one and only one value.

List different types of keys.

List of Keys:

Define Field.

A field is a unit of data consisting of one or more characteristics i.e ,Employee number Employee name or grade of an Employee in a record of the employee.

Give an example of entity.

Let us consider an example of "Students information System" which has entity like student,teacher,course list,scholarship,Time,labeling etc.Thus the entity involved in this case are same and the entity"student" can be defined in the form of database.

Define Primary key.

Primary key is a relation ,that attributes or a combination of attributes that uniquely identifies a row or a record.

What is Secondary Key?

A secondary key in non-unique field that is used as a secondary key.

Define an Entity.

An entity is anything about which you want to keep information in database.For example Students ,Teachers,etc.

Who is Database Administrator?

A database administrator is responsible for the entire data of an organization.Hr normally develops the overall functions requirements for the database being used in the office.He shares in developing the logical design for each database,He should control and manage the database,establish the data standard,supervise the data distribution within the organization and communicate with the user when necessary.

Define Foreign Key.

A foreign key is an attribute in a table whose value must match a primary key in another table.The table in which the foreign key is found in called dependent table and to which it refers is called parent table.

Define Composite Key.

Composite Key consists of two or more data elements or attributes,Invariably these are the same as Candidate/alternate keys except that of uniqueness requirement,In order to make it unique,assign STATUS or another attribute.

Define Alternate keys.

Sometimes it is not clear which field is to select as the primary key.There might exist some additional fields(or combination of fields) that also have the uniqueness property.These keys are termed as alternate key.

Who is end users?

The user or end-user is simply is a person who uses the computer for his specific need.He might have a moderate knowledge of computer,computer sciences and information technology and his need to use computers may be entertainment,education or professional task.

Differentiate between Primary key and Secondary key.

Primary Key:In a relation,the attributes the column or a combination of attributes that uniquely identifies a row or a record.