requests all in which the NAME is SMITH and the AGE field is greater than 35. The set of rules for constructing queries is known as a . Different DBMSs different query languages, although there is a semi-standardized query language called (structured query language). Sophisticated for managing database systems are called , or 4GLs for short.
The information from a database can be presented in a variety of formats. Most DBMSs include a program that enables you to in the form of a . Many DBMSs also include a component that enables you to output information in the form of graphs and charts.
Migrating from the manual and paper file set up is always an advantage in its own capacity. We shall highlight the major advantages of using a database or Data Base Management System in an organisation. Using a database will reduce both data redundancy and inconsistency. For larger or even smaller organisations like a small time starting estate agency, a database will promote sharing of data for example when referring to client files. Their rent or sales teams can share the information in order to be able to assist their clients better. Standards are enforced, through the use of the data dictionary or catalogue. Another advantage is that privacy and integrity controls are applicable to groups of users such as passwords and access controls for security. In-terms of privacy, a selection of authourised users can use the database and with reference to integrity, the database enables and promotes accurate input of data into the system. Data independency is also observed and by this we mean the immunity of applications to changes in storage structure and access strategy. Data accessibility and responsiveness is also very quick unlike the manual libraries or filing rooms.
However, as much as the database may have its adequate share of advantages, we also have to highlight on the disadvantages of this approach to organisations. Any company, institution or organisation embarking upon the automated database has to recruit specialised personnel, often new employees who have the know-how and are specialists in the computer or Information Technology field. In other cases the current employees undergo a lot of time on training, which then takes up a lot of production time. The database management system requires frequent back-up and clean up procedures to assist in the recovery of information. With regards to the sharing of data or information, as much as it may be advantageous to some organisations, this system tends to cause conflict and concurrency controls. This is usually the case with legal firms and doctors or general practitioners’ surgeries where most of their information is seriously confidential.
Databases can also be used effectively in different organisations if they relate to a certain models The different database models include hierarchical database model, network, relational and object oriented database models. The Hierarchical was used by early DBMS. Each record is related to others in a parent-child relationship or tree structure. Searching for a record involves moving progressively downward from a root and along the branches of the tree until the desired record is located. This system is probably useful to doctors as the information they requires involves an illness carried along from a parent or two generation earlier. Museums and other libraries may use this system as well. Universities and colleges would also find this model useful as it links students to their different courses, tutors, timetables and grades.
The network database model is a more complex structure. A record can be related to any number of other records. This model permits a record to be a member of more than one set at a time. It is less flexible because the relationship between records must be determined and implemented before a search can be conducted. The relational database model is the most widely used structure. Database packages based on this structure link records in different various tables to provide information to users. It is implementation independent in that it has logical representation and own set of terminology. It is relational in that one can access a customer number from an or customer file to identify the name and address of a customer. Primary keys are used to associate records.
In an object-oriented database model, each object is bound together with its own data and set of instructions that describes the behaviour and attributes of the objects. Every object is described by a set of attributes. For example the object building in a database of architectural drawing may have the attribute’s type, size, colour, just as in any other database. Every object has a set of procedures or set of methods. For instance, methods for an architectural drawing might include instructions to display, rotate or expand the drawing on a screen.
To conclude, we sum up by reiterating Masiiwa and Kabanda’s definition that a database is a logically coherent collection of data with some inherent meaning. By data, they mean the known facts that can be recorded and have implicit meaning. Organisations need this system or a DBMS in place because it stores tonnes of information that otherwise would be cumbersome to retrieve if everything was on lever arch files and papers and in employees offices.
- Kabanda, G. and Masiiwa, C. (2004) Management Information Systems, Module Comp102. Zimbabwe Open University. Harare
- Webopedia Computer Dictionary (2004) search engines.
- A:\Database merits & Demerits.doc
- October 5, 2004 12:04 PM