Structured Query Language is as database computer language that is designed to retrieve and manage data in relational database management systems (RDBMS), database schema creation and modification, and database object access control management. SQL is a programming language to query and modify data and to manage databases and was first standardized by the ANSI and later by the ISO. SQL also allows the retrieval, insertion, updating, and deletion of data. The first version of SQL was developed by IBM by Andrew Richardson, Donald C. Messerly and Raymond F. Boyce in the early 1970s. It was initially called SEQUEL and it was designed to manipulate and retrieve data that’s stored in IBM’s original relational database product. IBM patented their version of SQL in 1985 while the SQL language was officially standardized until 1986 by the American National Standards Institute (ANSI). Other versions of the SQL standard have been released by ANSI and as International Organization for Standardization (ISO) standards.
Examples:
- create a table
- create a view
- insert row
- update row
- delete row
Resources:
http://en.wikipedia.org/wiki/SQL
http://www.itl.nist.gov/div897/ctg/dm/sql_examples.htm
http://www.coderecipes.net/
Monday, April 6, 2009
METADATA
Metadata, or metainformation, means data about other data of any sort in any media. Content item or a collection of data including multiple content items and hierarchical levels are a few things that an item of metadata may describe. When it comes to data processing, metadata is considered like data that provides information about or documentation of other data that is managed within an application. This term should however be used with caution because all data is about something and is therefore metadata. Metadata can include descriptive information about the context, quality and condition, or characteristics of the data and it may be recorded with high or low granularity. Metadata provides context for data, it’s used to ease understanding, characteristics, and to manage the usage of the data. The metadata needed for effective data management differs with the type of data and context of use. For example, in a library, consists usually of data that is the content of the titles stocked, then metadata about a title would usually include a description of the content, the author the publication date and the physical location.
Examples of metadata:
- book
- photograph
- audio
- web page
Resources:
http://en.wikipedia.org/wiki/Metadata
Examples of metadata:
- book
- photograph
- audio
- web page
Resources:
http://en.wikipedia.org/wiki/Metadata
DBMS ADVANTAGES
When it comes to a DBMS many advantages can be described. The main advantages found throughout this internet research and that have come in many different websites are the following.
ADVANTAGES
-Controlling redundancy
-Providing storage structure for efficient query processing.
-Restricting unauthorized users.
-Providing concurrency.
-Providing backup and recovery.
-Enforcing integrity constraints.
When we talk about the advantage of the control of redundancy of data we mean that consistency is being obtained, no duplicates allowed. For example, if we want to update a specific data that is unique, an update to its value has to be executed only once, and the new value of the data is available to the users right away. With a controlled redundancy in the DBMS we get a system that will enforce the consistency of data as well. So if a data value is not unique and comes up more than once, the database will know to update all the occurrences of that data item in the database.
A DBMS has the advantage of enforcing integrity constraints if data is often accessed through the DBMS. For example, before you insert any kind of data, the DBMS can check if this type if data will be visible and available to all users of the system. If you need to insert salary information for a companies employee, your DBMS can check if the department still has enough budget, and it has not been exceeded.
Any business has advantages when using DBMS. An organization can use one type of database management system for the process of transactions that are made day by day and then have another DBMS on another computer that is used for random analysis and tasks.
Resources:
http://en.wikipedia.org/wiki/Database_management_system\
http://wiki.answers.com/Q/What_is_the_disadvantages_and_disadvantages_of_DBMS
http://www.ii.metu.edu.tr/~ion503/demo/chapter1/chapter15.htm
http://www.blurtit.com/q110246.html
http://estudents.co.cc/database-management-systems/advantages
ADVANTAGES
-Controlling redundancy
-Providing storage structure for efficient query processing.
-Restricting unauthorized users.
-Providing concurrency.
-Providing backup and recovery.
-Enforcing integrity constraints.
When we talk about the advantage of the control of redundancy of data we mean that consistency is being obtained, no duplicates allowed. For example, if we want to update a specific data that is unique, an update to its value has to be executed only once, and the new value of the data is available to the users right away. With a controlled redundancy in the DBMS we get a system that will enforce the consistency of data as well. So if a data value is not unique and comes up more than once, the database will know to update all the occurrences of that data item in the database.
A DBMS has the advantage of enforcing integrity constraints if data is often accessed through the DBMS. For example, before you insert any kind of data, the DBMS can check if this type if data will be visible and available to all users of the system. If you need to insert salary information for a companies employee, your DBMS can check if the department still has enough budget, and it has not been exceeded.
Any business has advantages when using DBMS. An organization can use one type of database management system for the process of transactions that are made day by day and then have another DBMS on another computer that is used for random analysis and tasks.
Resources:
http://en.wikipedia.org/wiki/Database_management_system\
http://wiki.answers.com/Q/What_is_the_disadvantages_and_disadvantages_of_DBMS
http://www.ii.metu.edu.tr/~ion503/demo/chapter1/chapter15.htm
http://www.blurtit.com/q110246.html
http://estudents.co.cc/database-management-systems/advantages
Thursday, April 2, 2009
DBMS ARCHITECTURE
There are a number of tasks that database architecture must handle. One of them is selecting which DBMS would best fit a newly developed application. Selecting the proper DBMS is not a simple task for there are different types of each DBMS for different architectures and purposes.A team consisting of business and IT experts will decide on the final architecture which will be based on the business needs of the organization.These are the four basic needs:
-entreprise
-departmental
-personal
-website
DBMS SOFTWARE EXAMPLES
-Oracle
Oracle is one of the world's most widely used DBMS. It is usually selected for large database projects and for high traffic websites. When it comes to efficiency data storing capability and reliability: database administrators swear by it.
-MySQL
The SQL Server DBMS runs on Windows Systems and is usually less expensive than competing DBMS. It is the most most popular open source database.
-Microsoft Access
Microsoft Access is a relational database management system from Microsoft that combines the relational Microsoft Jet Database Engine with a graphical user interface and software development tools. It is included in the higher versions for Windows, a member of the Microsoft Office suite of application and it is also sold seperatly.
Resources:
http://en.wikipedia.org/wiki/Database_management_system#Examples_of_Database_Management_Systems http://www.edumax.com/database-basics-understanding-dbms.html www.is.fsksm.utm.my/taib/upload_files/SCK2413/DBMS%20Architecture.ppt
DBMS HISTORY
A database management system (DBMS) is known as a computer software that is used to manage databases. They can use different variety of database models, like for example we have the network model and the relational model. For systems that are greater in size, a DBMS enables the users and the other software available to save and recover data in a prearranged manner. The database manager controls the management, storage space, organization and recovery of information in a selected database. DBMS are grouped according to their types or data structures. It can be seen as a group of previously written programs that are used to create, update and search a database. The DBMS allows requirements for data from the application program and informs the OS to transmit the appropriate data.
For the past thousands of years the saving of information as been done by different types of record keeping systems that had different form then the ones used today. In the past clay tablets, palm leaves, rocks, dances, music, and a variety of other media were used in order to save the data that was needed by the human. When technology evolved the keeping of records added a new media to save the data. A new media of data storage was created and used, the databases.Databases have been used since the beginning of the creation of computers. Older systems of databases were attached to the custom databases so that they could increase speed instead of flexibility, not like the new databases that we find now that can be applied to multiple needs. In the past DBMSs were available only to large organizations and businesses that had the necessary HW to support the large sets of data. In the 60’s, the first DBMS appeared. It was a time where projects of grand scale were being contemplated, organized and engineered, and it was the first time that such a large data set was being created in this new technology of computation. A DBMS was becoming needed since the data was more volatile than it used to be, and also because of the higher costs of data storage given by other medias. In the 80’s all the biggest vendors of HW systems that were large enough to support the growing needs of the growing organization of record keeping systems created a new DBMS with their own system solution. Hence, the first database management system sample was more vendors oriented. As usual, IBM was the first to get into this system, though competitors were growing in numbers as well as clones of databases solutions who were offering different entry points into the main target of the record keeping systems of organization.Throughout the years, the problems being solved by the IT management were growing with the technology itself, but no matter what the production systems of the organizations around the globe ran on year after year. Vendors of mainframe and mini-computer hardware increased incredibly, as well as the amount of peripheral types. Production sites were becoming a template of difficult tasks. The resolution of problems in the IT management was becoming more and more complex, and it was starting to involve many external groups of the organization.
Resources:
Database Management Systems, http://en.wikipedia.org/wiki/Database_management_system\
A Brief History of Modern RDBMS IT Management, Farmer Brown, http://www.mountainman.com.au/software/history/
Database and Database Users (chapter 1), http://www.ii.metu.edu.tr/~ion503/demo/chapter1/chapter12.htm
For the past thousands of years the saving of information as been done by different types of record keeping systems that had different form then the ones used today. In the past clay tablets, palm leaves, rocks, dances, music, and a variety of other media were used in order to save the data that was needed by the human. When technology evolved the keeping of records added a new media to save the data. A new media of data storage was created and used, the databases.Databases have been used since the beginning of the creation of computers. Older systems of databases were attached to the custom databases so that they could increase speed instead of flexibility, not like the new databases that we find now that can be applied to multiple needs. In the past DBMSs were available only to large organizations and businesses that had the necessary HW to support the large sets of data. In the 60’s, the first DBMS appeared. It was a time where projects of grand scale were being contemplated, organized and engineered, and it was the first time that such a large data set was being created in this new technology of computation. A DBMS was becoming needed since the data was more volatile than it used to be, and also because of the higher costs of data storage given by other medias. In the 80’s all the biggest vendors of HW systems that were large enough to support the growing needs of the growing organization of record keeping systems created a new DBMS with their own system solution. Hence, the first database management system sample was more vendors oriented. As usual, IBM was the first to get into this system, though competitors were growing in numbers as well as clones of databases solutions who were offering different entry points into the main target of the record keeping systems of organization.Throughout the years, the problems being solved by the IT management were growing with the technology itself, but no matter what the production systems of the organizations around the globe ran on year after year. Vendors of mainframe and mini-computer hardware increased incredibly, as well as the amount of peripheral types. Production sites were becoming a template of difficult tasks. The resolution of problems in the IT management was becoming more and more complex, and it was starting to involve many external groups of the organization.
Resources:
Database Management Systems, http://en.wikipedia.org/wiki/Database_management_system\
A Brief History of Modern RDBMS IT Management, Farmer Brown, http://www.mountainman.com.au/software/history/
Database and Database Users (chapter 1), http://www.ii.metu.edu.tr/~ion503/demo/chapter1/chapter12.htm
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