SQL is described by http://www.itl.nist.gov/div897/ctg/dm/sql_info.html
SQL is a popular relational database language first standardized in 1986 by the American National Standards Institute (ANSI). Since then, it has been formally adopted as an International Standard by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). It has also been adopted as a Federal Information Processing Standard (FIPS) for the U.S. federal government. (http://www.itl.nist.gov/div897/ctg/dm/sql_info.html accessed 18-10-2010)
My learning outcome from this session showed that SQL must be used in order to query databases and requires knowledge of exact syntax and structure in order to return exactly what the user wants. This implies that information must be entered into the table of a database with no ambiguity and similarly queries must be constructed exactly to return the required data.
Benefits to RDMSs
In trying to research the benfeits of the relation data model, I asked the question using wiki.answers.com (another type of query covered in information retrieval in the next blog.)
Answer:
- structural independence
- simplicity
- ad-hoc query capability
- easy to design
- security control
- non procedural access language
(http://wiki.answers.com/Q/What_are_the_benefits_of_relational_data_model Accessed 18-10-2010)
Database Management Systems such as Microsoft Access use a front end to enable a user with little or no knowledge of SQL to constuct queries using wizards and query builders, that add in features such as data validation to ensure data is entered correctly or queries are constructed correctly. This allows simplicity, easy design and non procedural access language.
Other RDBMS's used in commerically sensitive environments also must have the capability to hold data securely, allowing selective access to certain levels of information or restricting permissions for certain users. This will ensure the both the security of the data, through only allowing 'power users' to edit information and 'administrators' to control permissions and database maintenance tasks.
Other advantages over using the file approach: "Relational databases offer more robust reporting with report generators that filter and display selected fields. Relational databases offer the capability to build your own reporting modules. Most relational databases also offer the capability to import and export data from other software." http://www.databasedev.co.uk/flatfile-vs-rdbms.html Accessed 18-10-2010"
Limitiations to RDBMS
There are several limitaitons to the relational model for databases, a very sueful resouce : http://www.aspfree.com/c/a/Database/Introduction-to-RDBMS-OODBMS-and-ORDBMS/ Accessed 18-10-2010) provides a good few examples:
"There are limitations to the relational database management system. First, relational databases do not have enough storage area to handle data such as images, digital and audio/video. The system was originally created to handle the integration of media, traditional fielded data, and templates. Another limitation of the relational database is its inadequacy to operate with languages outside of SQL. After its original development, languages such as C++ and JavaScript were formed. However, relational databases do not work efficiently with these languages. A third limitation is the requirement that information must be in tables where relationships between entities are defined by values."
I understand from my work in the practical and my professional work in document management that the relationships between entities is the key to a successful database.
"Today, the relational model is the dominant data model as well as the foundation for the leading DBMS products, which include IBM’s DB2 family, Informix, Oracle, Sybase, Microsoft’s Access and SQLServer, as well as FoxBase and Paradox. RDBMS represent close to a multibillion-dollar industry alone." (http://www.aspfree.com/c/a/Database/Introduction-to-RDBMS-OODBMS-and-ORDBMS/ Accessed 18-10-2010)
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