What Is a Relational Database Management System?

Relational Database Management System (RDBMS) refers to a set of programs (database management system software) that include interconnected logical organization and access to these data. A relational database management system is a system that manages relational databases and logically organizes data.

Relational Database Management System (RDBMS) refers to a set of programs (database management system software) that include interconnected logical organization and access to these data. A relational database management system is a system that manages relational databases and logically organizes data.

Commonly used relational database management system products are Oracle, IBM's DB2 and Microsoft's SQL Server. ^[1]

Database design occupies a very important position in system development. The quality of database design directly affects the entire system.

The core of database design is data modeling, which is to build a data model of the real world for an application system development. The goal of database design is to build a database with little redundancy, easy maintenance and easy to use. Easy maintenance includes no occurrence of various operating abnormalities, and the security, consistency, and integrity of the database are also guaranteed; easy to use, in addition to being convenient to use, includes high access efficiency. ^[2]

Generally speaking, the database design process can be divided into three stages, namely conceptual design, logical design and physical design.

Concept Design

Concept design is to analyze the user's business activities, understand the user's use of the database, determine the user's requirements for the database and the database's integrity requirements.

The conceptual design phase can be divided into three steps, namely analyzing the entire user environment, determining the system boundary and analyzing the internal structure of the system.

1. Analyze the entire user environment, that is, understand the user's business activities from the perspective of data processing. To this end, data must be collected and surveyed accordingly. The survey mainly includes:

(1) The current business process in the organization, which reflects various data of the business process, such as bills, files, contracts, plans and statements, etc.

(2) Data elements and data processes. For data elements, it is necessary to investigate the nature of various data, the range of values, the providing department, the using department, the control authority, the confidentiality requirements, the frequency of use, and the connection between data. The data flow reflects the status of data processing activities, including the relationship between the data providing department, the processing department, and the data using department.

(3) The amount of data. Which are basic data and which are intermediate data.

(4) The user's data requirements and processing requirements for the computer, the output data and the situation of the output data, the required report form, etc.

Due to the limitations of user and designer expertise, it is best for users and designers to analyze and understand user needs together. At least the database designer is required to communicate with the user as much as possible and fully understand the user's processing requirements. This work is usually repeated many times. Finally, the designer draws a user activity diagram based on the user's data processing activity and obtains the user's permission. Based on the survey and analysis, a demand analysis description file is formed with the user as the final design inspection standard.

2. To determine the system boundary is to determine the scope of the computer system and its relationship with the external environment on the basis of investigating the status of information processing. This step must decide which processing activities are done by the system and which are still done manually. According to the system environment and conditions, system functions are proposed.

3. Analyze the internal structure of the system. That is to clarify all data requirements and processing requirements and their interrelationships. For data, all data items and their dependencies must be identified. For processing, all processing processes and their input and output data must be understood. Due to the complexity of this part of the work, a hierarchical decomposition method can be used to decompose the data processing process of the entire system into several small sub-processes, and then sub-process into smaller processes until it is easy to analyze. Each sub-processing process should be relatively independent, relatively simple to interconnect, clear in function, and clear in interface. Can be represented by a data flow diagram.

Next, we need to do a second piece of analysis, that is, to analyze the relationship between data and data, and analyze their relationship from the smallest data unit-data item.

The logical design of the database

Database logical design is to determine the logical structure of the entire database according to the requirements of the database and design theory, that is, determine which relationships (files) the entire database consists of, which attributes each relationship consists of, and so on.

According to the results of the requirements analysis, we already know the data items in the system and the dependencies between them (the relationship between the data). At this time, the logical design of the database can be completed with E-R diagrams and Smith diagrams (dependency diagrams) task.

Physical design of the database

The task of database physical design is to enable the logical structure of the database to be implemented on actual physical equipment. It is to use the existing physical storage equipment to effectively store data, that is, to determine the actual access mode and other details of the database. This step is different for different DBMS systems, and some are very complicated (such as hierarchical, network-type DBMS). For a relational DBMS, this step is relatively simple. For example, for FoxBASE system, the physical design process roughly includes: determining the type and length of each field, selecting the field to be indexed, etc. Other physical design work is done automatically by the system, and the designer need not worry about it. ^[3]