Databases |
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| 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, image. Other classification methods start from examining database models or database architectures. Software organizes the data in a database according to a database model.
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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. As of 2010 the relational model occurs most commonly. Other models such as the hierarchical model and the network model use a more explicit representation of relationships.
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Relational Database Management System (RDBMS) implements features of the relational model. In this context, Date's "Information Principle" states: "the entire information content of the database is represented in one and only one way. Namely as explicit values in column positions (attributes) and rows in relations (tuples). Therefore, there are no explicit pointers between related tables." This contrasts with the object database management system (ODBMS), which does store explicit pointers between related types.
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| RDBMS Components |
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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.
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SQL Engine - This component interprets and executes the SQL query. It comprises three major components (compiler, optimizer, and execution engine). |
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Transaction Engine - Transactions are sequences of operations that read or write database elements, which are grouped together. |
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Relational Engine - Relational objects such as Table, Index, and Referential integrity constraints are implemented in this component. |
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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. |
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