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concepts:rdbms
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Relational database management system

A relational database management system (RDBMS) is a database management system (DBMS) that stores databases based on the relational database model. The RDBMS places content into relationships and stores data in very simple structured database tables. It regulates administration of databases and regulates access to databases. DBMS always ensure database integrity by using the following constraints:

  • Domain Constraints determine dataypes/domains
  • Column Constraints determine sets of permissible values for a datatype/domain (for example: Primary Key, NOT NULL)
  • Entity Integrity Rules preclude that NULL is a permissible value for columns of a primary key
  • Referential Integrity Rules determine that every column containing a foreign key must have a values of the referenced primary key
  • Foreign Key Rules determine that the foreign key is equal to the primary key in some row of the referenced table

ANSI-SPARC Architecture

The ANSI-SPARC Architecture (American National Standards Institute, Standards Planning And Requirements Committee) is a standard reference model for DBMS that organizes data in three view based schemas:

  • The external schema models the data objects required by the applications (for example: „create view“ creates an external schema.
  • The conceptual schema describes the logical overall structure of the data (for example: „create table“ creates a conceptual schema).
  • The internal schema (physical data structure) describes the type and the composition of the used datastructure (records ) and specifies access paths and access mechanisms (for example: „create index“ creates an index for freely selectable access to data objects.

Every view takes over a specific part and represents a specific view on the data.

Relational database

A relational database is a collection of one or more two-dimensional tables (relations). A database table is composed of rows and columns. A row (tuple) represents a single set of data (record) and consists of attribute values. Attribute values are stored in table columns.

Examples

  • Attribute: depNumber, depName, employeeID
  • Attribute value: 1001, “IT”, 4711
  • Tuple: (1001, “IT”, 4711)
  • Relation: { (1001, “IT”, 4711), (1002, “Accounting”, 4712) }

Marketable products

  • Microsoft SQL Server by Microsoft Corp.
  • DB2 Enterprise Server by IBM Corp.
  • Oracle Database 11g by Oracle Corp.
  • MySQL Enterprise Edition Sun Microsystems / Oracle Corp.

References

Sumathi, S./ Esakkirajan, S.(2007): Fundamentals of Relational Database Management Systems, Springer Berlin Heidelberg

http://www.itwissen.info/definition/lexikon/relational-database-management-system-RDBMS-Relationales-Datenbank-Managementsystem.html

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concepts/rdbms.txt · Last modified: 2015/03/26 20:33 (external edit)