Metadata is data about data.
It is the way in which the database keeps information about its own structure.
Metadata is stored in the data dictionary.
Name Type Length Description Student Name Character 50 Student’s name Student ID Number 8 Unique identification number for a student Date of Birth Date 8 Student’s date of birth in the format ’01.01.80’
Metadata in Oracle SQL
SQL> DESC emp
Name Null? Type
EMPNO NOT NULL NUMBER(4)
Define metadata for data about the following:
Students in a college database
Books in a library system
Holidays booked by a person at a workplace
Try to think about what data needs to be kept -will it be a character, date or number?
Two-File Processing System
Two-File Processing System
The example used is of a car rental system.
One system processes CUSTOMER data, and the other processes RENTAL data.
Each of the files and the applications that use them are totally separate.
Although this is an improvement over older manual systems, there are a number of problems.
Problems in Two-File Processing System
1.Data are separated and isolated.
2.Data are often duplicated.
3.Problem of Data integrity
4.Application programs are dependent on file formats.
5.It is difficult to represent data in a user’s perspective.
Basic Structure of a Database
Database System in Detail
DBMS serves as intermediary
between user and the database by translating
user requests into the complex code required
to fulfill those requests.
Application programsmight be written in a programming
Language, such as Visual Basic or C++, or it might
be created through a DBMS utility e.g. Access’s forms wizard.
DBMS serves as intermediary between user and the database by translating user requests into the complex code required to fulfill those requests.
DBMS stands for data base management system. This is a software system which facilitates the formation, maintenance as well as use of an electronic database. It permits organizations to suitably develop databases for a range of applications by database administrators and certain specialists.
Features of the Database Approach
2.Reduced data duplication
4.Easier representation of users’ perspectives
•The DBMS is the software that handles all the interactions between applications and the database.
•Paul Benyon-Davis provides a useful way of looking at the structure of the DBMS itself i.e. DBMS Architecture.
Kernel, Interface and Toolkit
Central engine, which operates most of the core data management functions
The tools and applications that interact with the end-users.
These might be provided as part of the DBMS product or as separate piece of software.
It handles the interaction between the toolkit and the kernel
Advantages of DBMS
Control of data redundancy
Improved data integrity or Data consistency
Sharing of data
Enforcement of standards
Improved data accessibility and responsiveness
Improved backup and recovery services
Disadvantages of DBMS
Cost of DBMSs
Additional hardware costs
Cost of conversion
Requires skilled manpower