A database (DB) system is a computer-based record keeping system used to record and maintain certain types of information that have a significant value to some organization. A DB is a repository of stored data, which in general is both integrated and shared. Between the physical database and the users of the system is a layer of software, usually called the database management system (DBMS). All requests from the users to access the DB are handled by the DBMS.
When trying to organize the data and information within an organization, the DB helps the user in entering, storing, and retrieving it, and when trying to integrate all or part of the information of the enterprise the DB becomes a key player. Normally, within the DB, information is organized into data elements, fields, records, and files. In a system such as a hospital information system (HIS), a patient name is a data element or a field; a record could be related to that patient's visit on a particular date (e.g., date, diagnoses, treatments, charges, medications, tests) at a particular time; and a file would contain all the information from all the visits for that patient. An HIS DB will include not only patient files, but it could also have accounting information related to charges, inventory, payroll, and personnel records. With DB systems, different people can have access to different parts of the system, so, for example, not all personnel employees will have access to laboratory results.
The DBMS organization and definition of the contents of the individual data elements, fields, records, and files are provided via a machine-readable definition called "schema." This creates an independence of physical location from logical location of the content of a DB. The DBMS not only "manages the DB" but also allows for entering, editing, and retrieving results. The DBMS helps with the integration of data coming from multiple sources. The user can also access and retrieve specific types of information via queries.
A DB provides an organization with centralized control of its operational data. Some of the advantages of having centralized (versus distributed) control of the data are:
- Redundancies can be reduced.
- Inconsistencies can be avoided.
- Data can be shared.
- Standards can be enforced.
- Privacy, confidentiality, authenticity, and security restrictions can be applied.
- Integrity can be maintained.
- Conflicting requirements (among users) can be balanced (for the enterprise).
- Data is easier to support (the single repository, the application, and the endusers).
Due to technological advancements, databases today are much more complex than a few decades ago. They contain "multimedia" information, such as text, graphics, scanned images from documents, clinical images from all modalities (X-rays, ultra-sound, MRI, CT scan), still and dynamic studies, and sound. When doing population studies, the creation of data "warehouses" is necessary, and data "mining" techniques are used to extrapolate results. In public health, the data needed for a study can reside in a small computer, in a local area network (LAN), or in a wide area network (WAN). In order to use information that is geographically distributed (and/or with distributed users) it is important to learn techniques for data integration and data communications. Because of the continuing fusion of computers and communications, this is the fastest changing area within information technology.
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