Database types are divided according to data models. Data Model (Data Model) is an abstraction of data characteristics.
Data (Data) is a symbolic record that describes things, and model (Model) is an abstraction of the real world. (Recommended learning: MySQL Video Tutorial)
The data model describes the static characteristics, dynamic behavior and constraints of the system from an abstract level, providing an information representation and operation for the database system. Abstract frame. The content described by the data model has three parts: data structure, data operations and data constraints.
The content described by the data model includes three parts: data structure, data operations, and data constraints.
1) Data structure: It mainly describes the type, content, nature and relationship between data, etc. It is a collection of target types.
The target type is a component of the database and can generally be divided into two categories: data type and the relationship between data types.
Data types such as record types and data items in the DBTG (Database Task Group) network model, relationships and domains in the relational model, etc. The contact part includes the line types in the DBTG network model, etc. Data structure is the basis of data model, and data operations and constraints are basically based on data structure. Different data structures have different operations and constraints.
2) Data operations: Data operations in the data model mainly describe the operation types and operation methods on the corresponding data structure. It is a collection of operators, including several operations and inference rules, used to operate on a database composed of valid instances of the target type.
3) Data constraints: Data constraints in the data model mainly describe the syntax and word meaning connections between data in the data structure, the constraints and dependencies between them, and the rules for dynamic changes in data to ensure the stability of the data. Correct, valid and compatible. It is a collection of integrity rules to limit the database state and state changes that conform to the data model.
Constraint conditions can be divided according to different principles into data value constraints and data connection constraints; static constraints and dynamic constraints; entity constraints and reference constraints between entities, etc.
Three basic data models have been produced during the data development process, which are hierarchical model, network model and relational model.
These three models are named according to their data structures. The first two use formatted structures. In this type of structure, entities are represented by records, and records are abstracted as vertices of the graph.
The connection between record types is abstracted as the connection arc between vertices. The entire data structure corresponds to the graph. The basic structure of the hierarchical model is a tree structure; the basic structure of the network model is an undirected graph without any restrictions. The relational model is an unformatted structure that uses a single two-dimensional table structure to represent entities and the relationships between entities.
The most widely used is the relational model. Among the logical data types, the most commonly used ones are hierarchical model, network model and relational model.
For more MySQL related technical articles, please visit the MySQL Tutorial column to learn!
The above is the detailed content of How are database types classified?. For more information, please follow other related articles on the PHP Chinese website!

MySQLoffersvariousstorageengines,eachsuitedfordifferentusecases:1)InnoDBisidealforapplicationsneedingACIDcomplianceandhighconcurrency,supportingtransactionsandforeignkeys.2)MyISAMisbestforread-heavyworkloads,lackingtransactionsupport.3)Memoryengineis

Common security vulnerabilities in MySQL include SQL injection, weak passwords, improper permission configuration, and unupdated software. 1. SQL injection can be prevented by using preprocessing statements. 2. Weak passwords can be avoided by forcibly using strong password strategies. 3. Improper permission configuration can be resolved through regular review and adjustment of user permissions. 4. Unupdated software can be patched by regularly checking and updating the MySQL version.

Identifying slow queries in MySQL can be achieved by enabling slow query logs and setting thresholds. 1. Enable slow query logs and set thresholds. 2. View and analyze slow query log files, and use tools such as mysqldumpslow or pt-query-digest for in-depth analysis. 3. Optimizing slow queries can be achieved through index optimization, query rewriting and avoiding the use of SELECT*.

To monitor the health and performance of MySQL servers, you should pay attention to system health, performance metrics and query execution. 1) Monitor system health: Use top, htop or SHOWGLOBALSTATUS commands to view CPU, memory, disk I/O and network activities. 2) Track performance indicators: monitor key indicators such as query number per second, average query time and cache hit rate. 3) Ensure query execution optimization: Enable slow query logs, record and optimize queries whose execution time exceeds the set threshold.

The main difference between MySQL and MariaDB is performance, functionality and license: 1. MySQL is developed by Oracle, and MariaDB is its fork. 2. MariaDB may perform better in high load environments. 3.MariaDB provides more storage engines and functions. 4.MySQL adopts a dual license, and MariaDB is completely open source. The existing infrastructure, performance requirements, functional requirements and license costs should be taken into account when choosing.

MySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.

The situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.

In MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

Dreamweaver CS6
Visual web development tools
