RELATIONAL MODEL

1. Define the terms i) DDL ii) DML

DDL: Data base schema is specified by a set of definitions expressed by a special language

called a data definition language.

DML:

A data manipulation language is a language that enables users to access or manipulate data as organized by the appropriate data model

2. What is embedded SQL? What are its advantages? April/May-2011

Embedded SQL is a method of combining the computing power of a programming language and the database manipulation capabilities of SQL. Embedded SQL statements are SQL statements

written in line with the program source code of the host language. The embedded SQL

statements are parsed by an embedded SQL preprocessor and replaced by host-language calls to

a code library. The output from the preprocessor is then compiled by the host compiler. This allows programmers to embed SQL statements in programs written in any number of languages such as: C/C++, COBOL and Fortran

3. Write short notes on relational model

The relational model uses a collection of tables to represent both data and the relationships

among those data. The relational model is an example of a record based model.

4. Define tuple and attribute

• Attributes: column headers

• Tuple : Row

5. Define the term relation.

Relation is a subset of a Cartesian product of list domains.

6. Define tuple variable

Tuple variable is a variable whose domain is the set of all tuples.

7. Define the term Domain.

For each attribute there is a set of permitted values called the domain of that attribute.

8. What is a candidate key?

9. What is a primary key?

Primary key is chosen by the database designer as the principal means of identifying an entit y in

the entity set.

10. What is a super key?

A super key is a set of one or more attributes that collectively allows us to identify uniquely an entity in the entity set.

11. List the table modification commands in SQL?

Ø Deletion

Ø Insertion

Ø Updates

Ø Update of a view