关于一个MySQL的一个查询问题
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。

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

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)

Hot Topics



PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

One of the major changes introduced in MySQL 8.4 (the latest LTS release as of 2024) is that the "MySQL Native Password" plugin is no longer enabled by default. Further, MySQL 9.0 removes this plugin completely. This change affects PHP and other app

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

The page is blank after PHP connects to MySQL, and the reason why die() function fails. When learning the connection between PHP and MySQL database, you often encounter some confusing things...

CMS stands for Content Management System. It is a software application or platform that enables users to create, manage, and modify digital content without requiring advanced technical knowledge. CMS allows users to easily create and organize content
