– Data Base Files
– Data Mining and Warehousing
LEARNING OBJECTIVES
A database is a collection of related files that are usually integrated, linked or cross-referenced to one another. The advantage of a database is that data and records contained in different files can be easily organized and retrieved using specialized database management software called a database management system (DBMS) or database manager.
Data base and database management system are extensively used in all fields i.e. business, research, education, governance, audit etc.
Now the day is not far when database will be far ahead from software. Seeing the importance of database and DBMS, it becomes necessary for professionals like Company Secretaries to know basics concepts of data base and DBMS.
After reading this lesson, you should be able to:
– Understand the meaning of Data base, its types, advantages and disadvantages·
Know about basics of data structure – Define the term database management
system (DBMS), its objectives and functions
– Understand the meaning of Data Mining and data warehouse and their uses.
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Lesson 5
Database Management
The weaker the data available upon which to base one’s conclusion, the greater the precision which should be quoted in order to give the data authenticity.
Norman Ralph Augustine
DATABASE MANAGEMENT
Meaning of Database
Database is a collection of information organized in such a way that a computer program can quickly select desired pieces of data. One form of Database can be an electronic filing system.
Traditional databases are organized by fields, records, and files. A field is a single piece of information; a record is one complete set of fields; and a file is a collection of records. For example, a telephone book is analogous to a file. It contains a list of records, each of which consists of three fields: name, address, and telephone number.
To access information from a database, you need a database management system (DBMS). This is a collection of programs that enables you to enter, organize, and select data in a database.
Database is a collection of information that is organized so that it can easily be accessed, managed, and updated. In one view, databases can be classified according to types of content: bibliographic, full-text, numeric, and images.
In computing, databases are sometimes classified according to their organizational approach. The most prevalent approach is the relational database, a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways. A distributed database is one that can be dispersed or replicated among different points in a network. An object-oriented programming database is one that is congruent with the data defined in object classes and subclasses.
Computer databases typically contain aggregations of data records or files, such as sales transactions, product catalogs and inventories, and customer profiles. Typically, a database manager provides users the capabilities of controlling read/write access, specifying report generation, and analyzing usage. Databases and database managers are prevalent in large mainframe systems, but are also present in smaller distributed workstation and mid-range systems such as the AS/400 and on personal computers. SQL (Structured Query Language) is a standard language for making interactive queries from and updating a database such as IBM’s DB2, Microsoft’s SQL Server, and database products from Oracle, Sybase, and Computer Associates.
Characteristics of Data Base system (Differential features of database system w.r.t. file system)
There are a number of characteristics that distinguish the database approach with the file-based approach.1. Self-Describing Nature of a Database System
A Database System contains not only the database itself but also the descriptions of data structure and constraints (meta-data). This information is used by the DBMS software or database users if needed. This separation makes a database system totally different from the traditional file-based system in which the data definition is a part of application programs.
2. Insulation between Program and Data
In the file based system; the structure of the data files is defined in the application programs so if a user wants to change the structure of a file, all the programs that access that file might need to be changed as well. On the other hand, in the database approach, the data structure is stored in the system catalog not in the programs.
Therefore, one change is all that’s needed.
3. Support multiple views of data
A view is a subset of the database which is defined and dedicated for particular users of the system. Multiple users in the system might have different views of the system. Each view might contain only the data of interest to a user or a group of users.
4. Sharing of data and Multiuser system
A multiuser database system must allow multiple users access to the database at the same time. As a result, the multiuser DBMS must have concurrency control strategies to ensure several users access to the same data item at the same time, and to do so in a manner that the data will always be correct – data integrity.
5. Control Data Redundancy
In the Database approach, ideally each data item is stored in only one place in the database. In some cases redundancy still exists so as to improve system performance, but such redundancy is controlled and kept to minimum.
6. Data Sharing
The integration of the whole data in an organization leads to the ability to produce more information from a given amount of data.
7. Enforcing Integrity Constraints
DBMSs should provide capabilities to define and enforce certain constraints such as data type, data uniqueness, etc.
8. Restricting Unauthorized Access
Not all users of the system have the same accessing privileges. DBMSs should provide a security subsystem to create and control the user accounts.
9. Data Independence
System data (Meta Data) descriptions are separated from the application programs. Changes to the data structure is handled by the DBMS and not embedded in the program.
10. Transaction Processing
The DBMS must include concurrency control subsystems to ensure that several users trying to update the same data do so in a controlled manner. The results of any updates to the database must maintain consistency and validity.
11. Providing multiple views of data
A view may be a subset of the database. Various users may have different views of the database itself. Users may not need to be aware of how and where the data they refer to is stored.
12. Providing backup and recovery facilities
If the computer system fails in the middle of a complex update process, the recovery subsystem is responsible for making sure that the database is restored to the stage it was in before the process started executing.
13. Managing information
Managing information means taking care of it so that it works for us, and is useful for the work we are doing. The information we collect is no longer subject to “accidental disorganization” and becomes more easily accessible and integrated with the rest of our work. Managing information using a database allows us to become strategic users of the data we have.