BT0066-Database Management Systems

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Assignment

PROGRAM	B.Sc IT
SEMESTER	FIRST
SUBJECT CODE & NAME	BT0066-Database Management Systems
CREDIT	3
BK ID	B0950
MAX.MARKS	60

Note – Answer all questions. Each question is followed by evaluation scheme.

Q.1 what do you mean by entity and attributes in E-R diagram? Explain the importance of E-R diagram.

Answer: - Entity in E-R diagram:- An entity is something that exists in itself, actually or hypothetically. It need not be of material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate.

Sometimes, the word entity is used in a general sense of a being, whether or not the referent has material existence, e.g., is often referred to as an entity with no corporeal form (non-physical entity), such as a language. It is also often used to refer to ghosts and other spirits.

The word entitative is the adject

Q.2 Explain the following terms:

·         Relational database schema

·         Entity Integrity

·         Referential Integrity

·         Referential Integrity Constraints

Answer: - Relational database schema:- A database schema of a database system is its structure described in a formal language supported by the database management system (DBMS) and refers to the organization of data as a blueprint of how a database is constructed (divided into database tables in case of Relational Databases). The formal definition of database schema is a set of formulas (sentences) called integrity constraints imposed on a database. These integrity constraints ensure compatibility between parts of the schema. All

Entity Integrity: - In the relational data model, entity integrity is one of the three inherent integrity rules. Entity integrity is an integrity rule which states that every table must have a primary key and that the column or columns chosen to be the primary key should be unique and not NULL.[1]

Within relational databases using SQL,

Referential Integrity:- Referential integrity is a property of data which, when satisfied, requires every value of one attribute (column) of a relation (table) to exist as a value of another attribute in a different (or the same) relation (table).

For referential integrity to hold in a relational database, any field in a table that is declared a foreign key can contain either a null value, or only

Referential Integrity Constraints:- It refers to the integrity between master and detail table. If the information from the master table is deleted then the corresponding record from the detail table should also get deleted as this information has no meaning without master table.  Referantial integrity deals in parent-child relationship between tables.

Q.3 What do you mean by indexed sequential file organization? Explain with the help of an example.

Answer: - Indexed sequential file organization:-

·         An indexed file contains records ordered by a record key. Each record contains a field that contains the record key. The record key uniquely identifies the record and determines the sequence in which it is accessed with respect to other records. A record key for a record might be, for example, an employee number or an invoice number.

·         An indexed file can also use alternate indexes, that is, record keys that let you access the file using a different logical arrangement of

·          

Q.4 What is the system catalog in RDBMS? Also explain what information is stored in the system catalog.

Answer:- system catalog in RDBMS: The database catalog of a database instance consists of metadata in which definitions of database objects such as base tables, views (virtual tables), synonyms, value ranges, indexes, users, and user groups are stored.[1][2]

The SQL standard specifies a uniform means to access the catalog, called the INFORMATION_SCHEMA, but not all databases follow this, even if they implement other aspects of the SQL standard. For an example of database-specific metadata access methods, see Oracle metadata. -

What is stored in the catalog� -- an overview

·         Metadata

·          

Q.5 What do you mean by semantics of TRC queries? Give an example of TRC queries.

Answer:- semantics of TRC queries:- Tuple calculus is a calculus that was introduced by Edgar F. Codd as part of the relational model, in order to provide a declarative database-query language for this data model. It formed the inspiration for the database-query languages QUEL and SQL, of which the latter, although far less faithful to the original relational model and calculus, is now the de-facto-standard database-query language; a dialect of SQL is used by nearly every relational-database-management system. Lacroix and Pirotte proposed domain calculus, which is closer to first-order logic and which showed that both of these calculi (as well as

Q.6 Explain vertical framentation with the help of an example.

Answer: - Fragmentation:-Fragmentation involves breaking a relation (table) into two or more pieces either horizontally (Horizontal Fragmentation) or vertically (Vertical Fragmentation) or both (Hybrid), mainly to improve the availability of data to the end user and end user programs.

Let us start this section with an example. Consider XYZ bank, which is currently having around 1000 branches all over the country. Assume that it maintains its database at single location, say New Delhi (Head office - Central Site). Now the problem is that, all the requests generated from any part of the country can only be handled at the central site (Ne

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