一、数字类型
数字类型按照我的分类方法分为三类：整数类、小数类和数字类。
我所谓的“数字类”，就是指 DECIMAL 和 NUMERIC，它们是同一种类型。它严格的说不是一种数字类型，因为他们实际上是将数字以字符串形式保存的;他的值的每一位 (包括小数点) 占一个字节的存储空间，因此这种类型耗费空间比较大。但是它的一个突出的优点是小数的位数固定，在运算中不会“失真”，所以比较适合用于“价格”、“金额”这样对精度要求不高但准确度要求非常高的字段。
小数类，即浮点数类型，根据精度的不同，有 FLOAT 和 DOUBLE 两种。它们的优势是精确度，FLOAT 可以表示绝对值非常小、小到约 1.17E-38 (0.000...0117，小数点后面有 37 个零) 的小数，而 DOUBLE 更是可以表示绝对值小到约 2.22E-308 (0.000...0222，小数点后面有 307 个零) 的小数。FLOAT 类型和 DOUBLE 类型占用存储空间分别是 4 字节和 8 字节。如果需要用到小数的字段，精度要求不高的，当然用 FLOAT 了。可是说句实在话，我们“民用”的数据，哪有要求精度那么高的呢?这两种类型至今我没有用过
How do you alter a table in MySQL using the ALTER TABLE statement?Mar 19, 2025 pm 03:51 PMThe article discusses using MySQL's ALTER TABLE statement to modify tables, including adding/dropping columns, renaming tables/columns, and changing column data types.
How do I configure SSL/TLS encryption for MySQL connections?Mar 18, 2025 pm 12:01 PMArticle discusses configuring SSL/TLS encryption for MySQL, including certificate generation and verification. Main issue is using self-signed certificates' security implications.[Character count: 159]
How do you handle large datasets in MySQL?Mar 21, 2025 pm 12:15 PMArticle discusses strategies for handling large datasets in MySQL, including partitioning, sharding, indexing, and query optimization.
What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)?Mar 21, 2025 pm 06:28 PMArticle discusses popular MySQL GUI tools like MySQL Workbench and phpMyAdmin, comparing their features and suitability for beginners and advanced users.[159 characters]
How do you drop a table in MySQL using the DROP TABLE statement?Mar 19, 2025 pm 03:52 PMThe article discusses dropping tables in MySQL using the DROP TABLE statement, emphasizing precautions and risks. It highlights that the action is irreversible without backups, detailing recovery methods and potential production environment hazards.
How do you represent relationships using foreign keys?Mar 19, 2025 pm 03:48 PMArticle discusses using foreign keys to represent relationships in databases, focusing on best practices, data integrity, and common pitfalls to avoid.
How do you create indexes on JSON columns?Mar 21, 2025 pm 12:13 PMThe article discusses creating indexes on JSON columns in various databases like PostgreSQL, MySQL, and MongoDB to enhance query performance. It explains the syntax and benefits of indexing specific JSON paths, and lists supported database systems.
How do I secure MySQL against common vulnerabilities (SQL injection, brute-force attacks)?Mar 18, 2025 pm 12:00 PMArticle discusses securing MySQL against SQL injection and brute-force attacks using prepared statements, input validation, and strong password policies.(159 characters)
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
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
Atom editor mac version download
The most popular open source editor
Dreamweaver Mac version
Visual web development tools
Dreamweaver CS6
Visual web development tools
DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software
