Database Management Systems

Topics: Database management system, SQL, Database Pages: 27 (7809 words) Published: December 3, 2012
Database management systems

A database management system (DBMS) consists of software that operates databases, providing storage, access, security, backup and other facilities. Database management systems can be categorized according to the database model that they support, such as relational or XML, the type(s) of computer they support, such as a server cluster or a mobile phone, the query language(s) that access the database, such as SQL or XQuery, performance trade-offs, such as maximum scale or maximum speed or others. Some DBMS cover more than one entry in these categories, e.g., supporting multiple query languages. Examples of some commonly used DBMS are MySQL, PostgreSQL, Microsoft Access, SQL Server, FileMaker,Oracle,Sybase, dBASE, Clipper,FoxPro etc. Almost every database software comes with an Open Database Connectivity (ODBC) driver that allows the database to integrate with other databases. Definition of terms

What is Data?
Data is a collection of facts, such as values or measurements. It can be numbers, words, measurements, observations or even just descriptions of things. The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data (plural of "datum") are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which information and then knowledge are derived. Raw data, i.e. unprocessed data, refers to a collection of numbers, characters, images or other outputs from devices that collect information to convert physical quantities into symbols. Qualitative vs Quantitative

Data can be qualitative or quantitative.
• Qualitative data is descriptive information (it describes something) • Quantitative data, is numerical information (numbers). [pic]
And Quantitative data can also be Discrete or Continuous:
• Discrete data can only take certain values (like whole numbers) • Continuous data can take any value (within a range)
What is Information?
The word information is derived from Latin informare which means "give form to". The etymology thus connotes an imposition of structure upon some indeterminate mass. In the Oxford definition of the word it is connected both to knowledge and communication. Knowledge communicated concerning some particular fact, subject or event; that of which one is apprised or told; intelligence, news. Processed facts is what is known as information.

Desirable qualities of information

• Availability – Information should be available and accessible to those who need it. • Comprehensible – Information should be understandable to those who use it. • Relevance – Information should be applicable to the situations and performance of organizational functions. Relevant information is important to the decision maker. • Secure – Information should be secure from access by unauthorized users. • Usefulness – Information should be available in a form that is usable. • Timeliness - Information should be available when it is needed. • Reliability – Reliable information can be depended on. In many cases, reliability of information depends on the reliability of the data collection method. In other instances, reliability depends on the source of information. • Accuracy – Information should be correct, precise and without error. In some cases inaccurate information is generated because inaccurate data is fed into the transformation process (this is commonly called garbage in garbage out, GIGO). • Consistency– Information should not be self-contradictory. • Completeness – Complete information contains all the important facts. For example an investment report that does not contain all the costs is not complete. • Economical – Information should always be relatively economical to produce. Decision makers must always balance the value of information and the cost of producing it....
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