


Three tables, joint table query, can this SQL be further optimized?
SELECT c.username,c.sex,c.attentions,c.fans,a.id
,a.content
,a.isnum
,a.times
,a.turm
,a.keep
,a.comments
,a.uid
,b.mini
,b.mednum
,b.maxs
FROM (wb_userinfo c LEFT JOIN wb_weibo a ON c.uid = a.uid)
LEFT JOIN wb_picture b ON a.id
= b.wid
WHERE a.uid
IN(SELECT follow
FROM wb_follow WHERE fans
= 27) OR a.uid
= 27 ORDER BY a.times
LIMIT 0,10;
回复内容:
SELECT c.username,c.sex,c.attentions,c.fans,a.id
,a.content
,a.isnum
,a.times
,a.turm
,a.keep
,a.comments
,a.uid
,b.mini
,b.mednum
,b.maxs
FROM (wb_userinfo c LEFT JOIN wb_weibo a ON c.uid = a.uid)
LEFT JOIN wb_picture b ON a.id
= b.wid
WHERE a.uid
IN(SELECT follow
FROM wb_follow WHERE fans
= 27) OR a.uid
= 27 ORDER BY a.times
LIMIT 0,10;
有用or的可以考虑换成用union来尝试下
<code>(SELECT c.username,c.sex,c.attentions,c.fans,a.id,a.content,a.isnum,a.times,a.turm,a.keep,a.comments,a.uid,b.mini,b.mednum,b.maxs FROM (wb_userinfo c LEFT JOIN wb_weibo a ON c.uid = a.uid) LEFT JOIN wb_picture b ON a.id = b.wid WHERE a.uid IN(SELECT follow FROM wb_follow WHERE fans = 27) ) union (SELECT c.username,c.sex,c.attentions,c.fans,a.id,a.content,a.isnum,a.times,a.turm,a.keep,a.comments,a.uid,b.mini,b.mednum,b.maxs FROM (wb_userinfo c LEFT JOIN wb_weibo a ON c.uid = a.uid) LEFT JOIN wb_picture b ON a.id = b.wid WHERE a.uid = 27 ) ORDER BY a.times LIMIT 0,10;</code>
使用explain
看看分析报告贴出来看下,ref的值与row是的值索引使用情况等,连表查询的话我正常建议是拆成简单查询来。
就sql而言,可优化的空间不大,建议拆成若干条简单的sql,在代码里实现最终业务逻辑。
PS:尽量避免在sql里出现or
不要用join

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



The future of PHP will be achieved by adapting to new technology trends and introducing innovative features: 1) Adapting to cloud computing, containerization and microservice architectures, supporting Docker and Kubernetes; 2) introducing JIT compilers and enumeration types to improve performance and data processing efficiency; 3) Continuously optimize performance and promote best practices.

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.

You can open phpMyAdmin through the following steps: 1. Log in to the website control panel; 2. Find and click the phpMyAdmin icon; 3. Enter MySQL credentials; 4. Click "Login".

PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.

MySQL and SQL are essential skills for developers. 1.MySQL is an open source relational database management system, and SQL is the standard language used to manage and operate databases. 2.MySQL supports multiple storage engines through efficient data storage and retrieval functions, and SQL completes complex data operations through simple statements. 3. Examples of usage include basic queries and advanced queries, such as filtering and sorting by condition. 4. Common errors include syntax errors and performance issues, which can be optimized by checking SQL statements and using EXPLAIN commands. 5. Performance optimization techniques include using indexes, avoiding full table scanning, optimizing JOIN operations and improving code readability.

Redis uses a single threaded architecture to provide high performance, simplicity, and consistency. It utilizes I/O multiplexing, event loops, non-blocking I/O, and shared memory to improve concurrency, but with limitations of concurrency limitations, single point of failure, and unsuitable for write-intensive workloads.

PHP is not dying, but constantly adapting and evolving. 1) PHP has undergone multiple version iterations since 1994 to adapt to new technology trends. 2) It is currently widely used in e-commerce, content management systems and other fields. 3) PHP8 introduces JIT compiler and other functions to improve performance and modernization. 4) Use OPcache and follow PSR-12 standards to optimize performance and code quality.

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.
