Database Management | mr indian coder

 

A database management system (DBMS) is system software for creating and managing databases, allowing end users to create, protect, read, update and delete data in a database.

 

DATABASE MANAGEMENT

A Database consists of a number of tables. >The database oriented approach supports multiple views of the same data.

 

In database oriented approach, we store the common data in one table and access it from the required tables Multiple views of the same database may exist for different users

 

The logical level of abstraction defines the type of data that is stored in the database and the relationship between them. The design of the database is known as the database scheme.

 

The database administrator has the total control of the database and is responsible for setting up and maintaining the database. A data model is the methodology used by a particular DBMS to organize and access the data.

 

> Hierarchical, Network and Relational model are the three popular data models. Hierarchical Model:

(a) The hierarchical model was developed by IBM in 1968. (b) The data is organized in a tree structure where the nodes represent the records and the branches of the tree represent the

 

(c) Since the data is organized in a tree structure, the parent node has the links to its child nodes.

 

(d) If we want to search a record, we have to traverse the tree from the root through all its parent nodes to reach the specific record.

 

(e) The hashing function is used to locate the root (0) SYSTEM2000 is an example of hierarchical database.

 

Network Model:

(a) Recording of relationship in the network model is implemented by using pointers.

(b) Recording of relationship implementation is very complex since pointers are used.

 

(c) DBTG Codasyl was the first network database.

 

Relational Model:

(a) The Relational model, organizes data in the form of independent tables (consisting of rows and columns) that are related to each other

 

(b) A table consists of a number of rows (records/tuples) and columns (attributes).

 

(c) The degree of the table denotes the number of columns

(d) A domain in the relational model is said to be atomic, if it consists of indivisible units.

 

(e) A super key is a type of attribute that collectively identifies an entity in an entire set.

 

(f) A primary key is a set of one or more attributes that can uniquely identify the relationship keys relationship among data .

 

 

 

 

 

 

 

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