vu eng201 Mid Term Subjective Solved Past Paper No.7

Conceptual or Logical View:

This is the level of database architecture which contains the definition of all the data to be stored in the database and also contains rules and information about that structure and type of that data.

The conceptual view is the complete description of the data stored in the database. It stores the complete data of the organization that is why it is also known as the community view of the database. The conceptual view shows all the entities existing in the organization, attribute or characteristics associated with those entities and the relationships which exist among the entities of the organization.

DDL

It deals with the structure of database.The DDL (Data Definition Language) allows specification of not only a set of relations, but also the following information for each relation:

1. o The schema for each relation.
2. o The domain of values associated with each attribute.
3. o Integrity constraints.
4. o The set of indices for each relation.
5. o Security and authorization information.
6. o Physical storage structure on disk.

The Data Definition Language (DDL) contains the commands used to create and destroy databases and database objects. After the database structure is defined with DDL, database administrators and users can utilize the Data Manipulation Language to insert, retrieve and modify the data contained within it.

Data Manipulation Languages

This is the third component of relational data model. We have studied structure, which is the relation, integrity constraints both referential and entity integrity constraint. Data manipulation languages are used to carry out different operations like insertion, deletion or creation of database. Following are the two types of languages: "Student CGPA (StdCGPA) is identified through student name (StdName)"

Represent the above statement into the functional dependency (FD) notation.

For using a certain model certain data manipulations are performed using a specific language. This specific language is called data manipulation language.

Cartesian product

The Cartesian product needs not to be union compatible. It means they can be of different degree. It is denoted by X. suppose there is a relation R with attributes (A1, A2,...An) and S with attributes (B1, B2……Bn). The Cartesian product will be:

The resulting relation will be containing all the attributes of R and all of S. Moreover, all the rows of R will be merged with all the rows of S. So if there are m attributes and C rows in R and n attributes and D rows in S then the relations R x S will contain m + n columns and C * D rows. It is also called as cross product. The Cartesian product is also commutative and associative. For Example there are two relations COURSE and STUEDNT

COURSE

STUDENT

COURSE X STUDENT