Sunday, 4 March 2012

Database Basics

DataBase Management Systems (DBMS) -
Let us first understand the meaning of this overall term in installments of meaning of each of simple English words which make this term -
  • Data - The value of an attribute of an entity is called as Data. For example Age (attribute) of an employee (entity) is 49 (value). Every entity in the real world is described in terms of set of attributes and identified uniquely in terms of set of values of those attributes. For example refer to an ad of lost/found.
  • Base - Since there are several different entities (i.e. employees, departments, etc.) and multiple entities of same types (i.e. with common set of attributes, say all the employees), we always need to organize the data about them in some meaningful way which can allow us to access it easily. Such meaningful organization may be called as DataBase.
  • Management - Management is related to a facility or utility which allows to perform some operations or activity without causing any unpleasant side effect. For example a manager in an organization has to handle subordinate manpower in a way which should not cause any commotion, and yet get the target achieved for the department, or did you ever "managed" a traffic cop after you jumped a red signal and caught? Data is also subjected to manipulation and hence concept of management comes in to play to avoid any side effect arise from such manipulation.
  • System - System is a set of rules which allow the multiple users to share common resource, or in other words to ensure that every user gets a fair share of the common resource to utilize. For example we have a system of traffic lights so the commuters from all the direction can share the passage (square of streets) without causing a collusion. In computers the OS allows to share microprocessor, memory, data bus or storage to be shared among multiple competing processes.
 So now put together - A DBMS is set of rules (system) implemented through computer programs which allows to manipulate (manage) the values of attributes of several different types of entities organized in a meaningful way (DataBase).

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