MySQL中视图的使用及多表INNER JOIN的技巧_MySQL
bitsCN.com 做多表关联查询，如果表间关系非常清晰，结构简单，使用视图的方式比自己反复写复杂跨表SQL要容易的多 创建视图 Sql代码 CREATE VIEW view_name AS SELECT t1.xxx, t2.xxx, t3.xxx FROM (table1 t1 INNER JOIN table2 t2 ON t1.fid = t2.fid) INNER JOIN table3 t3 ON t1.mid = t3.mid; 这里使用了3表关联，对于多表关联的 INNER JOIN 写法有一个技巧1. 先写最简单的2表关联 INNER JOIN2. 然后使用 () 从 FROM 之后到语句结尾全部扩起来3. 在语句结尾开始连接与下一个表的 INNER JOIN记住这个原则，未来进行4表关联，5表关联就都不是什么难事了 删除视图 Sql代码 DROP VIEW view_name 作者 lj6684 bitsCN.com
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
1377
52
Win11 Tips Sharing: Skip Microsoft Account Login with One Trick
Mar 27, 2024 pm 02:57 PM
Win11 Tips Sharing: One trick to skip Microsoft account login Windows 11 is the latest operating system launched by Microsoft, with a new design style and many practical functions. However, for some users, having to log in to their Microsoft account every time they boot up the system can be a bit annoying. If you are one of them, you might as well try the following tips, which will allow you to skip logging in with a Microsoft account and enter the desktop interface directly. First, we need to create a local account in the system to log in instead of a Microsoft account. The advantage of doing this is
A must-have for veterans: Tips and precautions for * and & in C language
Apr 04, 2024 am 08:21 AM
In C language, it represents a pointer, which stores the address of other variables; & represents the address operator, which returns the memory address of a variable. Tips for using pointers include defining pointers, dereferencing pointers, and ensuring that pointers point to valid addresses; tips for using address operators & include obtaining variable addresses, and returning the address of the first element of the array when obtaining the address of an array element. A practical example demonstrating the use of pointer and address operators to reverse a string.
What are the tips for novices to create forms?
Mar 21, 2024 am 09:11 AM
We often create and edit tables in excel, but as a novice who has just come into contact with the software, how to use excel to create tables is not as easy as it is for us. Below, we will conduct some drills on some steps of table creation that novices, that is, beginners, need to master. We hope it will be helpful to those in need. A sample form for beginners is shown below: Let’s see how to complete it! 1. There are two methods to create a new excel document. You can right-click the mouse on a blank location on the [Desktop] - [New] - [xls] file. You can also [Start]-[All Programs]-[Microsoft Office]-[Microsoft Excel 20**] 2. Double-click our new ex
VSCode Getting Started Guide: A must-read for beginners to quickly master usage skills!
Mar 26, 2024 am 08:21 AM
VSCode (Visual Studio Code) is an open source code editor developed by Microsoft. It has powerful functions and rich plug-in support, making it one of the preferred tools for developers. This article will provide an introductory guide for beginners to help them quickly master the skills of using VSCode. In this article, we will introduce how to install VSCode, basic editing operations, shortcut keys, plug-in installation, etc., and provide readers with specific code examples. 1. Install VSCode first, we need
Oracle database query skills: get only one piece of duplicate data
Mar 08, 2024 pm 01:33 PM
Oracle database query skills: To obtain only one piece of duplicate data, specific code examples are required. In actual database queries, we often encounter situations where we need to obtain the only piece of data from duplicate data. This article will introduce how to use Oracle database techniques to obtain only one record in duplicate data, and provide specific code examples. Scenario Description Suppose we have a table named employee, which contains employee information. There may be duplicate employee information. We need to find all duplicates
Win11 Tricks Revealed: How to Bypass Microsoft Account Login
Mar 27, 2024 pm 07:57 PM
Win11 tricks revealed: How to bypass Microsoft account login Recently, Microsoft launched a new operating system Windows11, which has attracted widespread attention. Compared with previous versions, Windows 11 has made many new adjustments in terms of interface design and functional improvements, but it has also caused some controversy. The most eye-catching point is that it forces users to log in to the system with a Microsoft account. For some users, they may be more accustomed to logging in with a local account and are unwilling to bind their personal information to a Microsoft account.
PHP programming skills: How to jump to the web page within 3 seconds
Mar 24, 2024 am 09:18 AM
Title: PHP Programming Tips: How to Jump to a Web Page within 3 Seconds In web development, we often encounter situations where we need to automatically jump to another page within a certain period of time. This article will introduce how to use PHP to implement programming techniques to jump to a page within 3 seconds, and provide specific code examples. First of all, the basic principle of page jump is realized through the Location field in the HTTP response header. By setting this field, the browser can automatically jump to the specified page. Below is a simple example demonstrating how to use P
Tips for using Laravel form classes: ways to improve efficiency
Mar 11, 2024 pm 12:51 PM
Forms are an integral part of writing a website or application. Laravel, as a popular PHP framework, provides rich and powerful form classes, making form processing easier and more efficient. This article will introduce some tips on using Laravel form classes to help you improve development efficiency. The following explains in detail through specific code examples. Creating a form To create a form in Laravel, you first need to write the corresponding HTML form in the view. When working with forms, you can use Laravel
