Welcome to my “Types of relational database management system.”
Relational Database Management System (RDBMS) is a set of programs (database management system software) that includes interconnected logical organizations and access to these data. Relational database management system is the management of relational databases, and data logically organized the system.
Relational Database Management System (RDBMS) is a set of programs (database management system software) that includes interconnected logical organizations and access to these data. Relational database management system is the management of relational databases, and data logically organized the system.
Common relational database management system products are Oracle, IBM's DB2 and Microsoft's SQL Server.
Common relational database management system products are Oracle, IBM's DB2 and Microsoft's SQL Server.
Relational database design process
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Database design occupies a very important position in the system development, the quality of the database design directly affects the entire system.
At the heart of database design is data modeling, which is the development of a data model for the world of real data for an application. The goal of database design is to create a database that is less redundant, easier to maintain, and easier to use. Ease of maintenance includes no abnormal operation, and the security, consistency, and integrity of the database are also guaranteed. Ease of use includes higher access efficiency in addition to being convenient to use.
In general, the database design process can be divided into three stages, namely conceptual design, logical design and physical design.
Concept Design
Conceptual design is the analysis of the user's business activities to understand the user's use of the database to determine the user's requirements for the use of the database and the integrity of the database requirements.
Conceptual design phase can be divided into three steps, namely analysis of the entire user environment, to determine the system boundaries and analysis of the internal structure of the system.
1, analysis of the entire user environment from the perspective of data processing to understand the user's business activities. To do this, we must first collect the data and conduct the corresponding investigation. The survey mainly includes:
(1) Business processes within the current organization, reflecting various information about business processes such as bills, files, contracts, plans, and statements.
(2) data elements and data flow. For data elements, it is necessary to investigate the nature of the various data, the range of values, the departments, and departments used, the authority to control, confidentiality requirements, the frequency of use and the links between the data. The data flow reflects the data processing activities, including the relationship between the data provider department, processing department, and data usage department.
(3) the amount of data. What are the basic data, which is the intermediate data?
(4) the user's computer data requirements and processing requirements, the output data and output data, the required form of the report.
Due to the limitations of user and designer expertise, it is best to analyze and understand the needs of users by working together with designers and designers. At least require database designers try to communicate with users, fully understand the user's processing requirements. This work is usually repeated many times. Finally, the designer processes the activity based on the user's data, draws a map of the user's activity, and solicits the user's permission. On the basis of investigation and analysis, together with the user to form a demand analysis document, as the final design test.
2, to determine the system boundary In the investigation of information processing on the basis of the status quo, determine the scope of the computer system and its relationship with the external environment. This step must decide which processing activities are done by the system and which ones are still done by hand. According to the system environment and conditions, proposed system functions.
3, analyze the internal structure of the system. That is, to understand all the data requirements and processing requirements and their interrelationships. The data to identify all the data items and their dependencies between the processing to understand all the processing and their input and output data. Due to the complexity of this part of the work, we can use the method of hierarchical decomposition to decompose the data processing of the whole system into several small sub-processes and then break the sub-processes into smaller processes until the analysis is easy. Each sub-process to be relatively independent, interconnected relatively simple, clear function, clear interface. Can use the data flowchart to represent.
Next, we should do a second analysis, that is, to analyze the relationship between data and data, and to analyze their connection from the smallest data unit - data item.
Logical design of the database
Database logic design is based on the database requirements and design theory to determine the logical structure of the entire database, that is, to determine the entire database by which the relationship between the (file), each of the attributes by which attributes and so on.
According to the results of requirements analysis, we already know the data items in the system and the dependencies between them (the links between the data). At this time, the logical design of the database can be completed by E-R chart and Smith chart (dependency chart) task.
The physical design of the database
The task of database physics design is to make the logical structure of the database realized on the actual physical equipment, which is to utilize the existing physical storage equipment to store data effectively, that is to determine the actual access mode and other details of the database. This step varies by DBMS system, some very complex (such as hierarchical, network-based DBMS), while for relational DBMS, this step is relatively simple. For example, FoxBASE system, the physical design process includes: determine the type of each field, the length of the selected indexing field, and other physical design work done automatically by the system, designers do not have to worry about.
The relational database is based on the relational model of the database, with the help of mathematical concepts such as algebra and methods to deal with the data in the database. The various entities in the real world and the various connections between the entities are represented by the relational model. The relational model was first proposed by Edgar Cowdock in 1970 in conjunction with the "Cod 12th Law." Although there is some criticism of this model today, it is also the traditional standard for data storage. Standard Data Query Language SQL is a relational database-based language that performs the retrieval and manipulation of data in a relational database. The relational model consists of three parts: relational data structure, relational operation set, and relational integrity constraint.
Relationship model refers to the two-dimensional form model, so a relational database is composed of a two-dimensional table and the relationship between a data organization. The current mainstream relational database Oracle, DB2, PostgreSQL, Microsoft SQL Server, Microsoft Access, MySQL, Inspur K-DB and so on.
The Entity-Relationship Model, or ER Model for short, is a set of database design tools proposed by Dr. Peter PS Chen in 1976. He uses the notion of things and relationships in the real world to explain abstractions in the database Data structure. The entity relation model uses the graphic way (Entity-Relationship Diagram) to represent the conceptual design of the database, which helps to conceptualize and communicate the design process.
Relationship operation
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Relationship operation
Common operations in relational modules include:
data query
Select the projection connection and cross the difference in addition to the data operation to delete modify the query
Integrity
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Integrity constraints include:
Entity Integrity Referential Integrity User-defined integrity
SQL
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The SQL (Structured Query Language) is a structured query language proposed by Boyce and Chamberlin in 1974, which is between relational algebra and relational calculus. It is a universal and powerful relational database language.
Pattern structure
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Outer mode Inner mode
table
Main entry: database table
The form of rows and columns
The table is a collection of data organized in rows and columns. A database includes one or more tables. For example, there may be a table named authors about author information. Each column contains a specific type, such as the author's last name. Each line contains all the information about a specific author: name, address, and more. In a relational database, a table is a relationship, a relational database can contain multiple tables.
view
Main entry: view
index
Main entry: database index
Twelve guidelines
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All-inclusive systems should fully support all the features of the relational model. Edgar Crowd, the founder of the relational model, gives concrete examples of the basic rules to be followed in a total-relational system.
Guideline 0
A relational database management system must be able to manage the database entirely through its relational capabilities.
Guideline 1
Information Criteria All information in a relational database management system should be explicitly represented in the table as a value at the logical level.
Guideline 2
Guaranteed Access Guidelines rely on the combination of table name, main code, and column name to ensure that each data item in the relational database is logically accessed.
Guideline 3
Systematic processing of null values Relationship of the full relationship The database management system supports the concept of null values and handles the null values in a systematic way.
Guideline 4
Dynamic online data dictionary based on relational model The description of the database uses the same expressions as normal data at the logical level.
Guideline 5
A unified data sublanguage A relational database management system can have several languages and multiple terminal access methods but must have a language whose statements can be expressed as strictly grammatical strings and fully support various rules.
Guideline 6
View update guidelines All theoretically updatable views should also be allowed to be updated by the system.
Guideline 7
Advanced plug-in, modify and delete the operating system should be optimized for various operations query.
Guideline 8
Physical Independence of Data Applications and end-point activities remain logically invariant regardless of any changes made to the database representation or access method.
Guideline 9 Data Logical Independence Applications and end-point activities remain logically invariant when there is any change in the theoretical relationship that is not harmed in theory.
Guideline 10
The complete integrity of data The integrity constraints of a relational database must be defined in a database language and stored in a data dictionary.
Guideline 11
Distributed Independence Relational database management systems maintain the same logic when introducing distributed data or data redistribution.
Guideline 12
No damage guidelines If a relational database management system has a low-level language, then this low-level language cannot violate or bypass the integrity guidelines.
The Entity-Relationship Model, or ER Model for short, is a set of database design tools proposed by Dr. Peter PS Chen in 1976. He uses the notion of things and relationships in the real world to explain abstractions in the database Data structure. The entity relation model uses the graphic way (Entity-Relationship Diagram) to represent the conceptual design of the database, which helps to conceptualize and communicate the design process.
Relationship operation
edit
Relationship operation
Common operations in relational modules include:
data query
Select the projection connection and cross the difference in addition to the data operation to delete modify the query
Integrity
edit
Integrity constraints include:
Entity Integrity Referential Integrity User-defined integrity
SQL
edit
The SQL (Structured Query Language) is a structured query language proposed by Boyce and Chamberlin in 1974, which is between relational algebra and relational calculus. It is a universal and powerful relational database language.
Pattern structure
edit
Outer mode Inner mode
table
Main entry: database table
The form of rows and columns
The table is a collection of data organized in rows and columns. A database includes one or more tables. For example, there may be a table named authors about author information. Each column contains a specific type, such as the author's last name. Each line contains all the information about a specific author: name, address, and more. In a relational database, a table is a relationship, a relational database can contain multiple tables.
view
Main entry: view
index
Main entry: database index
Twelve guidelines
edit
All-inclusive systems should fully support all the features of the relational model. Edgar Crowd, the founder of the relational model, gives concrete examples of the basic rules to be followed in a total-relational system.
Guideline 0
A relational database management system must be able to manage the database entirely through its relational capabilities.
Guideline 1
Information Criteria All information in a relational database management system should be explicitly represented in the table as a value at the logical level.
Guideline 2
Guaranteed Access Guidelines rely on the combination of table name, main code, and column name to ensure that each data item in the relational database is logically accessed.
Guideline 3
Systematic processing of null values Relationship of the full relationship The database management system supports the concept of null values and handles the null values in a systematic way.
Guideline 4
Dynamic online data dictionary based on relational model The description of the database uses the same expressions as normal data at the logical level.
Guideline 5
A unified data sublanguage A relational database management system can have several languages and multiple terminal access methods but must have a language whose statements can be expressed as strictly grammatical strings and fully support various rules.
Guideline 6
View update guidelines All theoretically updatable views should also be allowed to be updated by the system.
Guideline 7
Advanced plug-in, modify and delete the operating system should be optimized for various operations query.
Guideline 8
Physical Independence of Data Applications and end-point activities remain logically invariant regardless of any changes made to the database representation or access method.
Guideline 9 Data Logical Independence Applications and end-point activities remain logically invariant when there is any change in the theoretical relationship that is not harmed in theory.
Guideline 10
The complete integrity of data The integrity constraints of a relational database must be defined in a database language and stored in a data dictionary.
Guideline 11
Distributed Independence Relational database management systems maintain the same logic when introducing distributed data or data redistribution.
Guideline 12
No damage guidelines If a relational database management system has a low-level language, then this low-level language cannot violate or bypass the integrity guidelines.
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