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This text explains the differences between database management systems (DBMS) and relational database management systems (RDBMS), as well as the importance of data models, cardinality, and the history of relational database theory. Large organizations often use multiple databases, with RDBMS being used for more complex applications. Flat files are not recommended for large operations and are not accepted in RDBMS design.
A database is a software application that allows for data storage. Within the database architecture there are different theories and implementations for storing physical data. A relational database management system (RDBMS) is a database that stores data in tables with relationships to other tables. By comparison, a database management system (DBMS) does not require defining relationships between tables. Both DBMS and RDBMS are models for storing information in a physical database.
Information is critical to competitive advantage in today’s business. Typically large organizations use multiple databases to perform business operations. These databases can include both large DBMSs and RDBMSs. Typically large sophisticated datasets require an RDBMS solution, while smaller collections of data can be managed with a DBMS.
A logical data model is a schema used to express data for an organization. Today, there are multiple techniques for creating a data model. A relational data model includes tables, keys, indexes, and foreign key relationships with other tables. Both DBMS and RDBMS support the concept of foreign keys, only RDBMS enforces such rules.
Cardinality is a mathematical term that explains the number of elements in a set. The cardinality relationship in a database explains the number of elements that can belong to a table with relationships. An example of cardinality is easily described with a person and phone numbers. Typically people have multiple phone numbers. This would be a one-to-many relationship in relational database theory.
Relational database theory was first introduced by Edgar Frank Codd in 1970. Within his theory Mr. Codd defined 13 rules, often called “Cod’s 12 rules” because he numbered them from zero to 12 , to satisfy a relational model. The relational model requires that an RDMS be built on the basis of relationships to other data within the data model.
Before a software application can be considered a database, it must have a mechanism for saving data to a physical device. This will allow other software to recover the saved data later. Both the DBMS and RDBMS allow this to happen.
A flat file is data of a logical ‘flat’ nature. This data has no relation to other data and requires programming logic to retrieve the records from a physical device. These file types are useful for simple lists, but are not recommended for large, complex operations. Flat file is allowed in DBMS design, but not accepted in RDBMS design.
Relational database design is the next generation ahead of database management system design. The relational database has used the fundamentals of DBMS as the basic model for data storage. DBMS and RDBMS are supported by most database vendors. Typically, RDBMS is used for more complex business applications.
