Table of Contents
回复内容:
Home Backend Development PHP Tutorial 关于一个MySQL的一个查询问题

关于一个MySQL的一个查询问题

Jun 06, 2016 pm 08:48 PM
mysql php

新手问个问题:

有三个表A、B、C

A是存储的文章里面有ID字段TITLE字段和CONTENT字段

B是一个连接A与C的表里面有AID和CID字段

C是一个存储A文章标签的表

我要通过A表里的ID查询出属于他的标签用

SELECT * FROM B WHERE AID = A.ID

然后用得到的数据再用同样方法查询C表

SELECT * FROM C WHERE ID = B.CID

因为我是初学MySQL所以不知道有没有更好的办法能一次查询就就可以完成我现在两部的工作?

回复内容:

新手问个问题:

有三个表A、B、C

A是存储的文章里面有ID字段TITLE字段和CONTENT字段

B是一个连接A与C的表里面有AID和CID字段

C是一个存储A文章标签的表

我要通过A表里的ID查询出属于他的标签用

SELECT * FROM B WHERE AID = A.ID

然后用得到的数据再用同样方法查询C表

SELECT * FROM C WHERE ID = B.CID

因为我是初学MySQL所以不知道有没有更好的办法能一次查询就就可以完成我现在两部的工作?

试试 :
假设A有个ID为10
SELECT * from C where C.ID in(select CID from B where AID=10)

也可以:
select C.tag from C right join B on C.ID=B.CID where B.AID=10

出于性能的考虑,十分建议分开查,然后用动态语言进行表间操作。
mysql跨表延迟会很高,当并发量上去了之后,就会出现各种意想不到的问题。

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

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

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Java Tutorial
1655
14
PHP Tutorial
1252
29
C# Tutorial
1226
24
Laravel Introduction Example Laravel Introduction Example Apr 18, 2025 pm 12:45 PM

Laravel is a PHP framework for easy building of web applications. It provides a range of powerful features including: Installation: Install the Laravel CLI globally with Composer and create applications in the project directory. Routing: Define the relationship between the URL and the handler in routes/web.php. View: Create a view in resources/views to render the application's interface. Database Integration: Provides out-of-the-box integration with databases such as MySQL and uses migration to create and modify tables. Model and Controller: The model represents the database entity and the controller processes HTTP requests.

Solve database connection problem: a practical case of using minii/db library Solve database connection problem: a practical case of using minii/db library Apr 18, 2025 am 07:09 AM

I encountered a tricky problem when developing a small application: the need to quickly integrate a lightweight database operation library. After trying multiple libraries, I found that they either have too much functionality or are not very compatible. Eventually, I found minii/db, a simplified version based on Yii2 that solved my problem perfectly.

The Continued Use of PHP: Reasons for Its Endurance The Continued Use of PHP: Reasons for Its Endurance Apr 19, 2025 am 12:23 AM

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

Laravel framework installation method Laravel framework installation method Apr 18, 2025 pm 12:54 PM

Article summary: This article provides detailed step-by-step instructions to guide readers on how to easily install the Laravel framework. Laravel is a powerful PHP framework that speeds up the development process of web applications. This tutorial covers the installation process from system requirements to configuring databases and setting up routing. By following these steps, readers can quickly and efficiently lay a solid foundation for their Laravel project.

MySQL and phpMyAdmin: Core Features and Functions MySQL and phpMyAdmin: Core Features and Functions Apr 22, 2025 am 12:12 AM

MySQL and phpMyAdmin are powerful database management tools. 1) MySQL is used to create databases and tables, and to execute DML and SQL queries. 2) phpMyAdmin provides an intuitive interface for database management, table structure management, data operations and user permission management.

MySQL vs. Other Programming Languages: A Comparison MySQL vs. Other Programming Languages: A Comparison Apr 19, 2025 am 12:22 AM

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages ​​such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages ​​have advantages in their respective fields such as data analytics, enterprise applications, and system programming.

Solve MySQL mode problem: The experience of using the TheliaMySQLModesChecker module Solve MySQL mode problem: The experience of using the TheliaMySQLModesChecker module Apr 18, 2025 am 08:42 AM

When developing an e-commerce website using Thelia, I encountered a tricky problem: MySQL mode is not set properly, causing some features to not function properly. After some exploration, I found a module called TheliaMySQLModesChecker, which is able to automatically fix the MySQL pattern required by Thelia, completely solving my troubles.

The Compatibility of IIS and PHP: A Deep Dive The Compatibility of IIS and PHP: A Deep Dive Apr 22, 2025 am 12:01 AM

IIS and PHP are compatible and are implemented through FastCGI. 1.IIS forwards the .php file request to the FastCGI module through the configuration file. 2. The FastCGI module starts the PHP process to process requests to improve performance and stability. 3. In actual applications, you need to pay attention to configuration details, error debugging and performance optimization.

See all articles