Chapter 6, Problem 6.1RQ

Program Plan Intro

(a)

Definition of Base Table.

Explanation of Solution

Base table in relational data model stores the raw data and correspond to the relations that are identified in the conceptual schema of the database.

Program Plan Intro

(b)

Definition of Data Definition Language

Explanation of Solution

Data Definition language (DDL) is a computer language which consists of various command used for creating and modifying databases and schemas. The commonly used DDL commands are CREATE, ALTER and DROP.

• CREATE command is used to create a new table with the following syntax

Create table Table name (Column definitions).

• ALTER command is used to modify the existing table. The syntax is:

Alter table Table name add new column.

• DROP command is used to delete a table. The syntax is:

Drop table Table name

Program Plan Intro

(c)

Definition of Data Manipulation language.

Explanation of Solution

Data Manipulation Language is a computer language used to modify the data in the databases. The most commonly used data manipulation commands are INSERT, DELETE and UPDATE.

• INSERT command is used to add records in the database. The syntax for INSERT command is:

Insert into table Table name(columns) values(values)

• DELETE command is used to delete records from the table according to the condition. Syntax is:

Delete from table Table name where(condition)

• UPDATE command is used to update the records in the database. Syntax is:

Update Table name set (column = value) where(condition)

Program Plan Intro

(d)

Definition of Dynamic view.

Explanation of Solution

Dynamic view is a kind of virtual table that is created as per request of user dynamically. Dynamic view cannot be considered as a temporary table. In fact, the definition of dynamic view is stored in the system catalog and as a result of SQL query, the content of the view is materialized.

Program Plan Intro

(e)

Definition of Materialized view

Explanation of Solution

Materialized view is different from Dynamic view. Here replicas and copies of data are created on the basis of SQL queries in the same manner as that of Dynamic views. Materialized views are stored physically on the disk.

Program Plan Intro

(f)

Definition of referential integrity constraint.

Explanation of Solution

Refential Integrity constraint is the concept used in relational database which ensures that the tables in the database are in consitent state. This statement means that if there is any foreign key used in the database, it must be in agreement with the primary key which is referenced from that foreign key. Any changes in primary key must be updated in the foreign key also.

Program Plan Intro

(g)

Definition of Relational DBMS

Explanation of Solution

Relational Database Management System (RDBMS) is a type of DBMS which is used for the data stored in relational databases in the form of tables(combunation of rows and columns). RDBMS is manily used to store the data related to manufacturing, finance, logistic and other applications. It uses SQL commands to access the daatbases.

Program Plan Intro

(h)

Definition of Schema.

Explanation of Solution

Schema is a structure or architecture of the database which is supported by the DBMS. It is considered as the blueprint of how the database is constructed. The schema is stored in the data dictionary generally by the database. It defines the objects in the databases.

Program Plan Intro

(i)

Definition of Virtual Table.

Explanation of Solution

Virtual table is constructed automatically as per the need of the DBMS and are not maintained as real data.