Database management system is a system is a computer software program that is designed as the means of managing all databases that are currently installed on a system hard drive or network. Different types of database management systems exist, with some of them designed for the oversight and proper control of databases that are configured for specific purposes. Here are some examples of the various incarnations of DBMS technology that are currently in use, and some of the basic elements that are part of DBMS software applications.
A Database Management System (DBMS) is a set of computer programs that controls the creation, maintenance, and the use of a database. It allows organizations to place control of database development in the hands of database administrators (DBAs) and other specialists. A DBMS is a system software package that helps the use of integrated collection of data records and files known as databases. It allows different user application programs to easily access the same database. DBMSs may use any of a variety of database models, such as the network model or relational model. In large systems, a DBMS allows users and other software to store and retrieve data in a structured way.fig 1.1 Instead of having to write computer programs to extract information, user can ask simple questions in a query language. Thus, many DBMS packages provide Fourth-generation programming language (4GLs) and other application development features. It helps to specify the logical organization for a database and access and use the information within a database. It provides facilities for controlling data access, enforcing data integrity, managing concurrency, and restoring the database from backups. A DBMS also provides the ability to logically present database information to users.
Databases have been in use since the earliest days of electronic computing. Unlike modern systems which can be applied to widely different databases and needs, the vast majority of older systems were tightly linked to the custom
databases in order to gain speed at the expense of flexibility. Originally DBMSs were found only in large organizations with the computer
hardware needed to support large data sets.Some types of DBMS are :
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1960s Navigational DBMS
As computers grew in speed and capability, a number of general-purpose database systems emerged; by the mid-1960s there were a number of such systems in commercial use. Interest in a standard began to grow, and Charles Bachman, author of one such product, Integrated Data Store (IDS), founded the "Database Task Group" within CODASYL, the group responsible for the creation and standardization of COBOL. In 1971 they delivered their standard, which generally became known as the "Codasyl approach", and soon there were a number of commercial products based on it available.
1970s Relational DBMS
Edgar Codd worked at IBM in San Jose, California, in one of their offshoot offices that was primarily involved in the development of hard disk systems. He was unhappy with the navigational model of the Codasyl approach, notably the lack of a "search" facility. In 1970, he wrote a number of papers that outlined a new approach to database construction that eventually culminated in the groundbreaking A Relational Model of Data for Large Shared Data Banks.
In this paper, he described a new system for storing and working with large databases. Instead of records being stored in some sort of linked list of free-form records as in Codasyl, Codd's idea was to use a "table" of fixed-length records. A linked-list system would be very inefficient when storing "sparse" databases where some of the data for any one record could be left empty. The relational model solved this by splitting the data into a series of normalized tables, with optional elements being moved out of the main table to where they would take up room only if needed.
Some differences between DBMSs
SQL(Structured query language) is a database computer language designed for managing data in relational database management systems (RDBMS), and originally based upon relational algebra. Its scope includes data insert, query, update and delete, schema creation and modification, and data access control. SQL was one of the first languages for Edgar F. Codd's relational model in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks" and became the most widely used language for relational databases.Fig 1.2
Always on Time
Marked to Standard
PHP(hypertext Prepocessor) provides a range of facilities to allow web database developers to retrieve data from a database and merge this dynamic content with static contect on a web paqe.
It includes the actual database(where the data are stored)and the DBMS,which manages all the access to the database,the application server manages communication with the databse server with the DBMS API.
Oracle DBMS Oracle database systemââ‚¬"identified by an alphanumeric system identifier or SIDââ‚¬"comprises at least one instance of the application, along with data storage. An instanceââ‚¬"identified persistently by an instantiation number comprises a set of operating-system processes and memory-structures that interact with the storage. In addition to storage, the database consists of online redo logs (or logs), which hold transactional history. Processes can in turn archive the online redo logs into archive logs (offline redo logs), which provide the basis (if necessary) for data recovery and for some forms of data replication.
The Oracle DBMS can store and execute stored procedures and functions within itself. PL/SQL (Oracle Corporation's proprietary procedural extension to SQL), or the object-oriented language Java can invoke such code objects and/or provide the programming structures for writing them.
DBMS stands for Database Management System which is a general term for a set of software dedicated to controlling the storage of data.
RDMBS stand for Relational DataBase Management System. This is the most common form of DBMS. Invented by E.F. Codd, the only way to view the data is as a set of tables. Because there can be relationships between the tables, people often assume that is what the word "relational" means. Not so. Codd was a mathematician and the word "relational" is a mathematical term from the science of set theory. It means, roughly, "based on tables.
fig 1.1 The different user application program can easily access the same database,it allows users and other software to sotre and retrieve data in structured way.
This chart shows several of the SQL language elements that compose a single statement.