What is a Database?

Hello Everyone!!

Most of us will be having an idea of what is a Database? But still lets rewind it again!!

A Database is an integrated collection of logically related records or files consolidated into a common pool that provides data for one or more multiple uses. One way of classifying databases involves the type of content, for example: bibliographic, full-text, numeric, and image. Other classification methods start from examining database models or database architectures. Software organizes the data in a database according to a database model. As of 2009 the relational model occurs most commonly. Other models such as the hierarchical model and the network model use a more explicit representation of relationships.

Database management systems


A database management system (DBMS) consists of software that organizes the storage of data. A DBMS controls the creation, maintenance, and use of the database storage structures of social organizations and of their users. It allows organizations to place control of organization wide database development in the hands of Database Administrators (DBAs) and other specialists. In large systems, a DBMS allows users and other software to store and retrieve data in a structured way.


Database management systems are usually categorized according to the database model that they support, such as the network, relational or object model. The model tends to determine the query languages that are available to access the database. One commonly used query language for the relational database is SQL, although SQL syntax and function can vary from one DBMS to another. A common query language for the object database is OQL; although not all vendors of object databases implement this, majority of them do implement this method. A great deal of the internal engineering of a DBMS is independent of the data model, and is concerned with managing factors such as performance, concurrency, integrity, and recovery from hardware failures. In these areas there are large differences between the products.

RDBMS components


• Interface drivers - A user or application program initiates either schema modification or content modification. These drivers are built on top of SQL. They provide methods to prepare statements, execute statements, fetch results, etc. Examples include DDL, DCL, DML, ODBC, and JDBC. Some vendors provide language-specific proprietary interfaces. For example MySQL provides drivers for PHP, Python, etc.

• SQL engine - This component interprets and executes the SQL query. It comprises three major components (compiler, optimizer, and execution engine).

• Transaction engine - Transactions are sequences of operations that read or write database elements, which are grouped together.

• Relational engine - Relational objects such as Table, Index, and Referential integrity constraints are implemented in this component.

• Storage engine - This component stores and retrieves data records. It also provides a mechanism to store metadata and control information such as undo logs, redo logs, lock tables, etc.

ODBMS components

• Language drivers - A user or application program initiates either schema modification or content modification via the chosen programming language. The drivers then provide the mechanism to manage object lifecycle coupling of the application memory space with the underlying persistent storage. Examples include C++, Java, .NET, and Ruby.


• Query engine - This component interprets and executes language-specific query commands in the form of OQL, LINQ, JDOQL, JPAQL, others. The query engine returns language specific collections of objects which satisfy a query predicate expressed as logical operators e.g. >, <, >=, <=, AND, OR, NOT, GroupBY, etc.

• Transaction engine - Transactions are sequences of operations that read or write database elements, which are grouped together. The transaction engine is concerned with such things as data isolation and consistency in the driver cache and data volumes by coordinating with the storage engine.

• Storage engine - This component stores and retrieves objects in an arbitrarily complex model. It also provides a mechanism to manage and store metadata and control information such as undo logs, redo logs, lock graphs.

Primary tasks of DBMS packages

• Database Development: used to define and organize the content, relationships, and structure of the data needed to build a database.


• Database Interrogation: can access the data in a database for information retrieval and report generation. End users can selectively retrieve and display information and produce printed reports and documents.

• Database Maintenance: used to add, delete, update, correct, and protect the data in a database.

• Application Development: used to develop prototypes of data entry screens, queries, forms, reports, tables, and labels for a prototyped application. Or use 4GL or 4th Generation Language or application generator to develop program codes.

In next blog we'll see about types of database. Have a wonderful weekend!!

Oracle!!

Hello Everyone.. Before we start with what is Oracle SQL, lets know who is Oracle.

Based in Redwood, California, Oracle Corporation is the largest software company whose primary business is database products. Historically, Oracle has targeted high-end workstations and minicomputers as the server platforms to run its database systems. Its relational database was the first to support the SQL language, which has since become the industry standard.


Along with Sun Microsystems, Oracle has been one of the leading champions of network computers.