如何提高数据库性能,减少数据库服务器压力瓶颈一两个小方法
树立的观念:一个SQL语句,如果在压力测试时CPU占有率达到100%,此语句肯定存在问题。 在大多数程序员的心里,一直认为数据库加索引,在查询中使用索引,就可以提高数据库性能。其实这种观点有一点的局限性,如果不好好的利用已经建立好的数据库索引,有时反
树立的观念:一个SQL语句,如果在压力测试时CPU占有率达到100%,此语句肯定存在问题。
在大多数程序员的心里,一直认为数据库加索引,在查询中使用索引,就可以提高数据库性能。其实这种观点有一点的局限性,如果不好好的利用已经建立好的数据库索引,有时反倒给数据库增加更大的处理压力。现在我们举例说明一下:
在现有的个人信息管理系统登录处的查询中,有这么一个SQL语句:
Select StudentInfoID, StudentNumber, StudentName,UnifyExamInfoID,NetSchoolID from StudentInfo
where StudentCrtificateNumber ='130425831217494' and rtrim(ltrim(StudentNumber)) = 'D0462382001'
此SQL语句的目的是查找这个考生是否存在,验证登录的效果,就是这么一个简单的SQL语句,在压力测试时,10个用户同时登录,就会造成数据库服务器 (2CPU,4G内存,IBM专用服务器)CPU占有率达到100%。而这张表也建立了StudentCrtificateNumber 和 StudentNumber 两个字段的索引, 问题出在哪呢?原因如下:
(1)在studentinfo表中,建立了一个索引LX_STUDENTINFO,包括了四个字段,顺序为:studycenternumber,studentnumber,studentname,studentcrtificatenumber。
(2)程序员理解的是,这个索引中包括了这两个字段,那么查询时就应该很快。实际不是。
大家注意一点,这个LX_STUDENTINFO索引,是四个索引字段,而他们的顺序 studycenternumber,studentnumber,studentname,studentcrtificatenumber,在数据库 设计中,如果查询采用的第一个字段和第二个字段组合,则该索引有效;如果查询采用第一个、第二个和第三个字段组合,该索引也有效;而如果第一个和第三个, 或第四个组合,则该索引是无效的,等同的效果仍是在没有索引的数据库中进行查询。也就是说建立的索引中的字段,在查询使用时,不能隔字段使用。
另外,索引中涉及到字段的顺序也会影响查询的性能,如果一个索引包含两个字段A1和A2,那么在查询时,一定要严格按索引中这两个字段的顺序设计查询,比 如:select * from a where A1='A' and A2='B'。而如果程序员写成了select * from a where A2='B' and A1='A'的话,虽然不影响程序正常使用,但会增加数据库的压力,并且查询效能会降低。
根据这种思路,重新调整了一下这个表的索引,在这个表中增加了一个新的索引,只包括这两个字段,并且按StudentCrtificateNumber 和StudentNumber先后顺序排序。经过300人同时登录的压力测试,CPU占有率才只占2-3%,证明调整结果有效。

InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

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.

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA


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

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

Hot Article

Hot Tools

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment