SOURCES:1- http://images.devshed.com/da/stories/Introduction%20to%20SQL/1.jpg
2- http://www.quackit.com/pix/database/tutorial/dbms_sql_server.gif
Monday, April 6, 2009
Posting 5- SQL
SOURCES:1- http://images.devshed.com/da/stories/Introduction%20to%20SQL/1.jpg
2- http://www.quackit.com/pix/database/tutorial/dbms_sql_server.gif
Posting 3- DBMS architectures
The main architecture of a DBMS is an entity. An entity is information that you collect data for. An Entity is like a table. Inside the table of information, the rows are records and the columns are attributes. Therefore, a record is a collection of related attributes about a certain entity. So when the data is entered in the database, each unit of data is called a "record". Every single record is unique and it is further "broken down" (1) to a different number of fields which are also known as attributes. Having only data in a database is useless. The data must be related and organize in such ways to create useful information for companies.In order to associate data, relationships must be formed by either a one-to-many relationship, one-to-one or many-to-many relationship. One-to-many relationship means for example a person can play for one team but a team has many players. One-to-one relationship means that a girl has 1 boyfriend and the boy has 1 girlfriend. Many-to-many relationship means that each supplier supplies many different companies and the company has many suppliers. Besides the relationships, in order to make a relation, each record must have a primary key which becomes an foreign key in an attribute of another record. Examples of DBMS softwares are Microsoft Access, FoxPro and DataEase.
Source: 1- http://www.referenceforbusiness.com/encyclopedia/Cos-Des/Database-Management-Systems.html
2- http://www.mountainman.com.au/software/history/intro.html
3- http://www.opensplice.com/image-upload/DBMS_Connect6.jpg
Posting 2- Advantages of DBMS
The Advantages of DMBS in business and other organizations are its flexibility, its speed and its space advantage compared to a system with an ineffective database or a manual database. A DBMS has the ability to analyze information in many different ways so that its faster when you need to look for information in a database for your firm. The DMBS can automate specific information from hundreds to millions of different entries within seconds. Compare to physical database, a computerized DBMS saves a lot of space because data is stored in computers that are related through a network instead of having files stored in a big wareshouse.
Besides the speed, a computerized database can eliminate all the errors and problems that manual recorded databases tend to create. It basically emiminates the probability of having inconsistent data for your business. Another advantage of having an information systems is that you can base yourself with these information from your databases and learn from your actions, mistakes and success in order for your organization to improve and adapt to the rapid changing world.
For example when a firm's accountant wants to calculate the cost of the goods sold for an international company at a particular month; with the help of a DBMS, the accountant can have access to accurate purchase information from another store in another continent instantsly. Instead of manually handwritting the request and send it out to the other store which would take more time and this method also won't have the flexibility and easiness of access compare to a DBMS. Another example would be when an accountant has to do a balance sheet for a company, the accountant would have all the information from the DBMS in a better arrangement, easier to locate and more efficient to computer the balance of the firm at a particular month. Without the DBMS, the information may be more difficult to locate and arranged inefficiently.
Besides the speed, a computerized database can eliminate all the errors and problems that manual recorded databases tend to create. It basically emiminates the probability of having inconsistent data for your business. Another advantage of having an information systems is that you can base yourself with these information from your databases and learn from your actions, mistakes and success in order for your organization to improve and adapt to the rapid changing world.
For example when a firm's accountant wants to calculate the cost of the goods sold for an international company at a particular month; with the help of a DBMS, the accountant can have access to accurate purchase information from another store in another continent instantsly. Instead of manually handwritting the request and send it out to the other store which would take more time and this method also won't have the flexibility and easiness of access compare to a DBMS. Another example would be when an accountant has to do a balance sheet for a company, the accountant would have all the information from the DBMS in a better arrangement, easier to locate and more efficient to computer the balance of the firm at a particular month. Without the DBMS, the information may be more difficult to locate and arranged inefficiently.
SOURCE: 1- http://db.cs.berkeley.edu/topics/lecs/dbprimer/tsld011.htm
2- http://estudents.co.cc/database-management-systems/advantages
Posting 1- History of DataBase Management Systems
A database is a collection of data that is properly organized and it can be easily searched and manipulated. Data is basically raw material that is recorded but its unformatted information. Data is the most fundamental element in any information system and raw data has no meaning by itself. Data must be stored, organize and manage within a database in order to have a meaning and be useful information. DBMS are applications that are created to store, update and retrieve information in efficiently in very little time within a database.
Before DataBase Management Systems were created, organizations kept large numbers of databases on different punched cards. When needed, the data was searched manually and sorted by a tabulating equipment. But the word database only existed in the mid 1960s when computers stored data sequentially on magnetic tape. Computers enabled quick random access to data inside a database. The early database systems were develop for mainframe computers but the computers could only handle a single data file at a time and the computer was programmed for specific data-processing functions which meant that when a database was used for inventory, the same database could not be used for product purchases. So Information Technology researchers began to do research and develop systems that can record transactions as they occur rather then on a daily batch.
Later on in the mid 1970s, information systems were develop in such ways that they can handle multiple functions within different files. But the only negative feedback about the database was that it was hard to navigate and to relate all these different databases with multiple functions. In order to fix this problem, researchers introduced the relational database management systems which basically gave relationship between different databases in order to link all the databases together to make it more effective for organizational use.
From then on, database management systems became more and more complex and sophisticated in order to satisfy the complex needs of different firms. Today, all databases are created, stored and manipulated by computers and all the databases are related through a network.
Source: 1- http://www.referenceforbusiness.com/encyclopedia/Cos-Des/Database-Management-Systems.html#HISTORY
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