How can database approach improve the limitations of file-based system? Can you identify at least one advantage of database approach compared to file-based approach? Well, the database approach emphasizes the integration and sharing of data throughout the organisation which means that all departments should be able to integrate and share the same data. The detail advantages of database approach is explained below.
1. Program-data independence
With database approach, data descriptions are stored in a central location called the repository, separately from the application program. Thus, it allows an organisationÊs data to change and evolve without changing the application programs that process the data. What this means is that the changing of data would be easier and faster.
2. Planned data redundancy and improved data consistency
Ideally, each data should be recorded in only one place in the database.
Thus, a good database design would integrate redundant data files into a
single logical structure. In this case, any updates of data would be easier and faster. In fact, we can avoid wasted storage space that results from redundant data storage. By controlling data redundancy, the data would also be consistent.
3. Increased productivity of application development
A database approach reduces the cost and time for developing new database applications. What this means is that with the same database, different applications can be developed. Thus, there is no need to design and develop a new database for different applications (Hoffer, et. al. 2007).
1.3.1 The Database
Can you recall the definition of database? It is a shared collection of logically related data, and a description of this data, designed to meet the information needs of an organisation (Connoly and Begg, 2005). In other words, it is a large repository of data that can be used by many users at the same time. It is also defined as a self-describing collection of integrated records because it consists of a description of the data. The description of the data is called system catalog or data dictionary of metadata (Connoly and Begg, 2005).
The database approach separates the structure of the data from the application programs and this approach is known as data abstraction. Thus, we can change the internal definition of an object in the database without affecting the users of the object, provided that the external definition remains the same. For instance, if we were to add a new field to a record or create a new file, then the existing applications are unaffected. More examples of this will be shown in the next Topic.
Some other terms that you need to understand are entity, attribute and relationships. An entity is a specific object (for example a department, place, or event) in the organisation that is to be represented in the database. An attribute is a property that explains some characteristics of the object that we wish to record.
A relationship is an association between entities (Connoly and Begg, 2005).
Figure 1.5 illustrates an example of an Entity-Relationship (ER) diagram for part of a department in an organisation.
Figure 1.5: An example of Entity-Relationship diagram
By referring to Figure 1.5, we can see that it consists of two entities (the rectangles), that are, Department and Staff. It has one relationsip, that is, has, where it indicates that a department has many staffs. For each entity, there is one attribute, that is, Department No and StaffNo. In other words, the database holds data that is logically related. More explanations on this will be discussed in later Topics.
SELF-CHECK 1.3
1. What is metadata?
2. Define entity, attribute and relationships.
1.3.2 The Database Management Systems (DBMS)
Now, what about DBMS? Can you recall the definition of DBMS from earlier explanation? „A DBMS is a software that interacts with the userÊs application programs and the database‰ (Connoly and Begg, 2005). Initially, DBMSs provide efficient storage and retrieval of data. But, as the marketplace and innovation demands increase, DBMSs have evolved to provide broad range of features for data acquisition, storage, dissemination, maintenance, retrieval and formatting which make the DBMSs more complex.
Let us now discuss in detail some of the common features of DBMS.
Database definition
In defining a database, the entities stored in tables (an entity is defined as a cluster of data usually about a single item or object that can be accessed) and relationships that indicate the connections among the tables must be specified.
Most DBMSs provide several tools to define databases. The Structured Query Language (SQL) is an industry standard language supported by most DBMSs that can be used to define tables and relationships among tables (Mannino 2001).
More discussions on SQL will be in later Topics.
Nonprocedural access
The most important feature of DBMSs is the ability to answer queries. A query is a request to extract useful data. For instance, in a student DBMS where a few tables may have been defined, like personal information table and result table and a query might be a request to list the names of the students who will be graduating next semester. Nonprocedural access allows users to submit queries
by specifying what parts of a database to retrieve (Mannino 2001). More discussions on queries will be in later Topics.
Application development
Most DBMSs provide graphical tools for building complete applications using forms and reports. For instance, data entry forms provide an easy way to enter and edit data. Report forms provide easy to view results of a query (Mannino 2001).
Transaction processing
Transaction processing allows a DBMSs to process large volumes of repetitive work. A transaction is a unit of job that should be processed continously without any interruptions from other users and without loss of data due to failures. An example of a transaction is making an airline reservation. The user does not know the details about the transaction processing other than the assurance that the process is reliable and safe (Mannino 2001).
Database tuning include a few monitoring processing that could improve the performance. Utility programs can be used to reorganize a database, select physical structures for better performance and repair damaged parts of a database. This feature is important for DBMSs that support large databases with many simultaneous users and usually known as Enterprise DBMSs. On the other hand, desktop DBMSs run on personal computers and small servers that support limited transaction processing features usually use by small businesses (Mannino 2001).