DBMS Database

DBMSA database is an organized collection of data. A relational database is a collection of schemes, tables, queries, reports, views, and other elements. A database management system (DBMS) is a computer software application that interacts with end users, other applications, and the database itself to capture and analyze data. A general-purpose DBMS allows the definition, creation, querying, update, and administration of databases.

Database management system vs file system DBMS file system

Large no. of files used. Less no. of files used. Better security, username, and password Does not provide security. Redundancy problem is solved as data is independent. Data redundancy is a problem loss of integrity. Data access take lots of time. It takes less time. Vast permanent design Little preliminary design.

Characteristics of Database Approach

• Representing the aspects of real-world application A Database represents the features of the real-world application.
• According to this, change in the real world will be reflected in the database.
• Managing Information An information is very helpful for whatever work we do so Database take care of its information. Management of information using Database makes us deliberated user of data.
• Easy Operational Implementation Makes it Powerful All the operations like insert, delete, update, search etc used in the database are carried out in a flexible and easy way. A user with some knowledge can easily perform these operations which makes it powerful.
• Self Describing Nature A database must be of self-describing itself, that narrate and describe itself and which contains a description of the whole database.
• Logical Relationship Between Records And Data This helps the user to access various records depending upon the logical conditions by a single query from the database.

DBMS architecture data model

A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to properties of the real world entities. The term data model is used in two distinct but closely related senses. Sometimes it refers to an abstract formalization of the objects and relationships found in a particular application domain. A data model explicitly determines the structure of data. Data models are specified in a data modeling notation, which is often graphical in form. A data model can sometimes be referred to as a data structure, especially in the context of programming languages. Data models are often complemented by function models, especially in the context of enterprise models.

The role of data models

The main aim of data models is to support the development of information systems by providing the definition and format of data. According to West and Fowler (1999) "if this is done consistently across systems then compatibility of data can be achieved. If the same data structures are used to store and access data then different applications can share data.

Three perspectives

A data model instance may be one of three kinds according to ANSI in 1975:

• Conceptual data model: describes the semantics of a domain, being the scope of the model. For example, it may be a model of the interest area of an organization or industry. This consists of entity classes, representing kinds of things of significance in the domain, and relationship assertions about associations between pairs of entity classes. A conceptual schema specifies the kinds of facts or propositions that can be expressed using the model. In that sense, it defines the allowed expressions in an artificial 'language' with a scope that is limited by the scope of the model.
• Logic data model: describes the semantics, as represented by a particular data manipulation technology. This consists of descriptions of tables and columns, object-oriented classes, and XML tags, among other things.
• Physical data model: describes the physical means by which data are stored. This is concerned with partitions, CPUs, tablespaces, and the like. The significance of this approach, according to ANSI, is that it allows the three perspectives to be relatively independent of each other. Storage technology can change without affecting either the logical or the conceptual model.

Instances and schemas

Design of a database is called the schema. The schema is of three types: Physical schemalogical schema view schema. The design of a database at a physical level is called physical schema, how the data stored in blocks of storage is described at this level. Design of database at a logical level is called logical schema, programmers and database administrators work at this level, at this level data can be described as certain types of data records gets stored in data structures, however the internal details such as implementation of data structure is hidden at this level (available at physical level). Design of database at view level is called view schema. This generally describes end-user interaction with database systems. The data stored in the database at a particular moment of time is called an instance of the database. The database schema defines the variable declarations in tables that belong to a particular database; the value of these variables at a moment of time is called the instance of that database.