DBMS

What is DBMS ?

DBMS :- Is a collation of related records and a set of  programs that access and manipulate these records. DBMS enables user to enter,store  and manage this data.
In DBMS the data was stored in the flat file format .So,the information about different objects was maintained separately in different physical files.The relation between these objects to be maintained in a separate physical file.Thus a single package would consist of too many files and wholesome programming to integrate them into a single system.
Solution to these problems are centralized database system.In this system the database is stored in the central location.Every user can access to the common database which is stored in central location from there machine.


 C. J. Date :- An authority on database technology defines a database system.as computer based record keeping system whose overall purpose is to record and maintain information.
We use a filing cabinet and paper files to file our papers.They provide centralized control of data.when we have new paper to be filed, we add those sheet s to a file.Old unwanted papers can be removed.
Changes can be made to existing files.when a particular document or paper is required it can be accessed.
A database management system is similar to this filing cabinet.it is as an electronic filing cabinet,which besides storing also allows addition,deletion,modification and retrieval of data.

RDBMS

 RDBMS is relational database management system which is provide a relational mode between data tables.
It is a suite of software programs for creating, modifying and manipulating a relational database.
Dr.E F Codd was unhappy with the DBMSs available in those days handled large volume of data.He presented his paper titled "A Relational Mode Of Data for  large Shared Databanks".It is based on two  branches of mathematics - 'Set Theory' and 'Order Predicate Logic'.
It has 12 Rules :-

1. All information represented only in tables.
2. Each atomic value is accessible by combination of table name, primary key and column name.
     >>  No duplicates. 
3. Systematic treatment of NULLs.
4. Line data catalog maintained.
    >> Accessible in same way as ordinary data.
5. Comprehensive data sub-language.
    >>   Data definitions.
    >>   View definitions.
    >>   Data manipulation.
    >>   Integrity constrains.
    >>   Authorization.
    >>   Transaction boundaries.
6. View updated correctly.
7. High-level Insert, Update, Delete.
8. Physical data independence.
9. Logical data independence.
10.Integrity independence.
     >> Not in application program.
     >> Semantic integrity a near-impossibility here.
11.Distribution independence.
12.Non-Subversion.
     >> Low-level Language can't subvert to bypass high-level language.