In the daily development process, we need to operate the Mysql database, which involves the construction of tables. How to create a well-structured database table requires following the following three database paradigms.
1. The first normal form
ensures the atomicity of each column (field) in the data table.
If each field in the data table is the smallest data unit that cannot be further divided, it satisfies the first normal form.
For example: user table, containing fields id, username, password
2. The second normal form
is in the second normal form Going one step further on the basis of normal form, the goal is to ensure that every column in the table is related to the primary key.
If a relationship satisfies the first normal form and all other columns except the primary key depend on the primary key, it satisfies the second normal form.
For example: a user has only one role, and one role corresponds to multiple users. Then you can establish the data table relationship as follows to make it meet the second normal form.
User user table, fields id, username, password, role_id
role role table, fields id, name
The user table is associated with the role table through the role id (role_id)
3. The third normal form
is a step further based on the second normal form. The goal is to ensure that the columns in the table are directly related to the primary key. Relevant, not indirect.
For example: one user can correspond to multiple roles, and one role can also correspond to multiple users. Then you can establish the data table relationship as follows to make it meet the third normal form.
user user table, fields id, username, password
role role table, field id, name
user_role user-role intermediate table, id ,user_id,role_id
Like this, the relationship between the user table and the role table is established through the third table (intermediate table), and at the same time it conforms to the principle of normalization, it can be called the third normal form.
4. Denormalization
Denormalization refers to improving the read performance of the database by adding redundant or duplicate data.
For example: Add the field role_name to the user_role user-role intermediate table in the above example.
Denormalization can reduce the number of join tables during related queries.
The above is the table creation paradigm for MYSQL database that I have compiled. I hope it will be helpful to everyone in the future.
Related articles:
MySQL index optimization covering index
Mysql field type selection method
The connection between mysql locks and indexes
The above is the detailed content of Database three normal forms and anti-normal forms. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
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
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
iOS 18 adds a new 'Recovered' album function to retrieve lost or damaged photos
Jul 18, 2024 am 05:48 AM
Apple's latest releases of iOS18, iPadOS18 and macOS Sequoia systems have added an important feature to the Photos application, designed to help users easily recover photos and videos lost or damaged due to various reasons. The new feature introduces an album called "Recovered" in the Tools section of the Photos app that will automatically appear when a user has pictures or videos on their device that are not part of their photo library. The emergence of the "Recovered" album provides a solution for photos and videos lost due to database corruption, the camera application not saving to the photo library correctly, or a third-party application managing the photo library. Users only need a few simple steps
How to save JSON data to database in Golang?
Jun 06, 2024 am 11:24 AM
JSON data can be saved into a MySQL database by using the gjson library or the json.Unmarshal function. The gjson library provides convenience methods to parse JSON fields, and the json.Unmarshal function requires a target type pointer to unmarshal JSON data. Both methods require preparing SQL statements and performing insert operations to persist the data into the database.
MySQL: Simple Concepts for Easy Learning
Apr 10, 2025 am 09:29 AM
MySQL is an open source relational database management system. 1) Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2) Basic operations: INSERT, UPDATE, DELETE and SELECT. 3) Advanced operations: JOIN, subquery and transaction processing. 4) Debugging skills: Check syntax, data type and permissions. 5) Optimization suggestions: Use indexes, avoid SELECT* and use transactions.
Detailed tutorial on establishing a database connection using MySQLi in PHP
Jun 04, 2024 pm 01:42 PM
How to use MySQLi to establish a database connection in PHP: Include MySQLi extension (require_once) Create connection function (functionconnect_to_db) Call connection function ($conn=connect_to_db()) Execute query ($result=$conn->query()) Close connection ( $conn->close())
How to handle database connection errors in PHP
Jun 05, 2024 pm 02:16 PM
To handle database connection errors in PHP, you can use the following steps: Use mysqli_connect_errno() to obtain the error code. Use mysqli_connect_error() to get the error message. By capturing and logging these error messages, database connection issues can be easily identified and resolved, ensuring the smooth running of your application.
Oracle's Role in the Business World
Apr 23, 2025 am 12:01 AM
Oracle is not only a database company, but also a leader in cloud computing and ERP systems. 1. Oracle provides comprehensive solutions from database to cloud services and ERP systems. 2. OracleCloud challenges AWS and Azure, providing IaaS, PaaS and SaaS services. 3. Oracle's ERP systems such as E-BusinessSuite and FusionApplications help enterprises optimize operations.
MySQL: An Introduction to the World's Most Popular Database
Apr 12, 2025 am 12:18 AM
MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.
MySQL vs. Other Databases: Comparing the Options
Apr 15, 2025 am 12:08 AM
MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.
