Loading

DBMS

Definition :

Database is a collection of data. DBMS is a software used to manage DB in efficient way.

Flat File System

A flat file database is a type of database that stores data in a single table. Flat file databases are generally in plain-text form, where each line holds only one record. The fields in the record are separated using delimiters such as tabs and commas.
Flat File System

Disadvantage of flat file system
1) Data Security : The data stored in the flat files can be easily accessible and hence it is not secure.
2) Data Redundancy : In this storage model, the same information may get duplicated in two or more files. This may lead to to higher storage and access cost. it also may lead to data inconsistency.
3) Data Isolation : Data Isolation means that all the related data is not available in one file. Usually the data is scattered in various files having different formats. Hence writing new application programs to retrieve the appropriate data is difficult.
4) Lack of Flexibility : If we need unanticipated data, huge programming effort is needed to make the information available.
5) Concurrent Access Anomalies : Many traditional systems allow multiple users to access and update the same piece of data simultaneously & this concurrent updates may result in inconsistent data.
These difficulties lead to the development of database systems.

Database Management System

Using a DBMS to manage data has many advantages:

Advantage of Database Management System
1) Efficient Data Access
2) Data Integrity and Security
3) Concurrent Access and Crash Recovery
4) Reduced Application Development Time

Levels of Abstraction

Levels of Abstraction
Physical level : Describes how a record is stored
Logical level : Describes data stored in database, and the relationships among the data
View level : A way to hide details of data types and information for security purposes.

Important Terms

  • There are two types of Data Manipulation Languages (DML), Structured Query Language (SQL) and Data Definition Language (DDL). DML are computer languages also known as query language, it is used for accessing and working on the data.
  • Data redundancy : It means there are no duplications of data. No multiple files of the same kind.
  • Data dictionary : It is like a normal dictionary, but containing metadata.
  • Metadata : It contains information about all the data in the DBMS.
  • The Keys :
    Primary key is used to identify a particular or specific record (file). It is unique to a particular file.
    Foreign Key makes a connection between a component (field) in one table with a component identified by a primary key.
  • Relational database : is the kind of database model, where there are logical connections between the various files, which are kept in tables.