Database and DBMS
A database is a collection of related information about a subject that is organized in a useful manner that provides a basis or basis for the procedure, such as information retrieval, conclusion drawing and decision making.
A database is a collection of interrelated data of some place or person or things in such a way that an application program such as DBMS can easily access it.
A DBMS is a collection of programs that handle files from the database. The DBMS allows access to the files, modified records and retrieved data as requested. The DBMS acts as an interface between the application program and the data in the data base. Examples: Microsoft Access, Oracle, MySQL, SQL Server etc.
Traditional file system was used from the beginning to manage data on a computer. In the conventional file system the data can be duplicated, they can not be exchanged and confidentiality and integrity can not be protected in a very good manner. It is often extremely difficult to search for the data. Therefore it is not easy to work in file system where everything is stored in file.
Advantage and Disadvantage of DBMS
DBMS (Database Management System)
A DBMS is a set of programs which administer the database files. The DBMS lets you access the files. Update the records, gather data as requested. The DBMS acts as an interface between the application program and the data in the data base.
Objectives of DBMS
• To provide storage area for the pertinent mass of data.
• To make the data easy to use for the end user.
• Giving prompt response to user requests for data.
• To make the latest modification available to the database as soon as possible.
• Data redundancy elimination (data duplication).
• So multiple users can be active on the same time.
• To protect the data against physical damage and unauthorized access.
Advantage of DBMS
1. Data Sharing: Data may be stored in a database and shared. For example, with a DBMS, the data for the entire business is essentially made available to all managers and end-users who need it.
2. Reduced data Redundancy: In traditional file it is possible to duplicate the processing of the same data many times, or places are also called redundancy. A DBMS cuts down database duplication.
3. Integrity can be maintained: Integrity ensures the data contained in a database is reliable or consistent. Hence the integrity issue is the issue of ensuring that the data in the database is correct.
4. Data Independence: The DBMS will keep data description separate from the application that uses the data. Therefore changes in the data definition can occur without requiring changes in any application program that uses the data.
5. Security can be enforced: There should be lots of confidential data in an organization; not all users should have access to such data. In a DBMS, some security restrictions may be applied by giving different authority to different users.
6. Providing multiple user interface: DBMS gives different user interfaces.
Disadvantage of DBMS
1. Initial investment is high for implementing DBMS.
2. Proper training is required in the database system for the employees to work properly.
3. When there is some fault in one part of the database it also affects the other parts.
4. It is complex to understand and implement.
5. Overhead cost to provide functional security, recovery, and integrity.
6. Cost for hardware maintenance, software, backup, recovery and upgrading to it remains forever.
Database Model Notes
Data model describes the structure of a database. Data model is the gathering of conceptual tools to describe data, relationships etc.
Types of Database Model
1. Hierarchical Database Model
Logically, model records are arranged into a hierarchy of links within a hierarchical database. It is arranged logically in an inverted tree pattern. It is based on child as a parent. A parent record may have multiple children but only one parent may have a child.
• A hierarchical database model is a data model in which the data is organized into a tree-like structure.
• The hierarchical model of data is the oldest type of data model which IBM created in 1968.
• Records are interlinked by tree-like or hierarchical structures.
• A parent may have multiple children but only one parent may have a child.
• Relationships one to one and relationships one to many.
• It is the easiest database model.
• This increases data reliability because the same database owner becomes more protected and no one else can access and change a child at different locations without having to contact their parent.
• If the parent is known it is quick and easy to search.
• It is very successful at managing ‘one-to-many’ relationship.
• It helps in building complicated system from basic components.
• The database model is old fashioned, outdated.
• This is a non-flexible database model (Modification and child inclusion without consulting the parent is unlikely, or very complicated process).
• It can not handle relationships ‘Many — to-Many.’
• It increases data consistency, because different locations can store the same data.
• When the parent node is deleted, all the kids nodes are automatically deleted.
2. Network Data Model
• Network Database Model Network database model is a modified Hierarchical Database version.
• In the network database structure each node may have multiple parents.
• Operation and maintenance of this structure becomes complicated as the number of points in the network increases.
• This is less user friendly compared to the hierarchical structure.
• It Support Many to Many Relationship
• It is more flexible than the hierarchical model, because it accepts the relationship between ‘many to many.’
• This eliminates redundancy so data should not be replicated if the same data is required.
• Multidirectional pointers make quick searches.
• It is one of the database’s complex models.
• Relationships require to handle larger programs.
• Compared to the hierarchical model it is less secure, as it is open to all.
3. Entity Relation Data Model
• The ER data models are based on a perception of the real world, consisting of a collection of basic objects called entities, and the relationship between them.
• The database can be modelled as a collection of entities, and the relationship between entities.
• An E-R diagram can be used to graphically represent the overall logical structure of a database.
Basic Component of Diagram
• Rectangle (represent entity sets)
• Ellipses (represents attributes)
• Diamonds (represent relationship sets among entity sets)
• Lines (link attributes to entity sets and entity sets to relationship sets)
4. Relational Database Model
In a two-dimensional table, data is arranged in a relational Database model, which is easy for a user to develop and understand. This type of model is also describable in mathematical terms. Since many managers often work with tabular form data, most easily understand the structure used in a relational database.
• Since it is linked to others on the table, some common fields and rules implemented on one table can be easily implemented onto another table.
• There is even little consistency in data.
• Data standardization is necessary.
• Rapid data base processing is possible
• Complexer than other models.
• Too many rules makes database non-user-friendly
Language used to interact with data base management systems is called the language of the database. DBMS contains two languages: