如上图这个sql 。cjPrice是600 cjNum是5.97 这种情况下
上面的sql算出的是3581.9998741149902 而计算器算出的是3582
而我用phpmyadmin执行如下sql 得到的也是3582 到底什么问题啊
select sum(600*5.97) 这也是3582
请问到底怎么解决啊~~~
回复讨论(解决方案)
如果你的 cjNum 不是 DECIMAL 类型的，那么应用 round 取结果
字段类型用的是 float 吧
单精度不准确
对精度要求高的话，建议换成double、decimal、numeric
double双精度，效率上差一点，但准确性高
decimal和numeric几乎等价，必须指定具体精度
你的查询结果是跟你那相乘的两个字段类型有关的
cjPrice整型 cjNum Float型
在phpmysql 下执行，是与mysql计算一样的，有小数位的。
估计和版本有关系吧，
可以试试 select round(SUM(cjPrice*cjNum), 2) from ..
保留两位小数
的确，我的cjPrice是decimal cjNum是float 我把 cjNum也改成decimal就行了
How to make PHP applications fasterMay 12, 2025 am 12:12 AMTomakePHPapplicationsfaster,followthesesteps:1)UseOpcodeCachinglikeOPcachetostoreprecompiledscriptbytecode.2)MinimizeDatabaseQueriesbyusingquerycachingandefficientindexing.3)LeveragePHP7 Featuresforbettercodeefficiency.4)ImplementCachingStrategiessuc
PHP Performance Optimization Checklist: Improve Speed NowMay 12, 2025 am 12:07 AMToimprovePHPapplicationspeed,followthesesteps:1)EnableopcodecachingwithAPCutoreducescriptexecutiontime.2)ImplementdatabasequerycachingusingPDOtominimizedatabasehits.3)UseHTTP/2tomultiplexrequestsandreduceconnectionoverhead.4)Limitsessionusagebyclosin
PHP Dependency Injection: Improve Code TestabilityMay 12, 2025 am 12:03 AMDependency injection (DI) significantly improves the testability of PHP code by explicitly transitive dependencies. 1) DI decoupling classes and specific implementations make testing and maintenance more flexible. 2) Among the three types, the constructor injects explicit expression dependencies to keep the state consistent. 3) Use DI containers to manage complex dependencies to improve code quality and development efficiency.
PHP Performance Optimization: Database Query OptimizationMay 12, 2025 am 12:02 AMDatabasequeryoptimizationinPHPinvolvesseveralstrategiestoenhanceperformance.1)Selectonlynecessarycolumnstoreducedatatransfer.2)Useindexingtospeedupdataretrieval.3)Implementquerycachingtostoreresultsoffrequentqueries.4)Utilizepreparedstatementsforeffi
Simple Guide: Sending Email with PHP ScriptMay 12, 2025 am 12:02 AMPHPisusedforsendingemailsduetoitsbuilt-inmail()functionandsupportivelibrarieslikePHPMailerandSwiftMailer.1)Usethemail()functionforbasicemails,butithaslimitations.2)EmployPHPMailerforadvancedfeatureslikeHTMLemailsandattachments.3)Improvedeliverability
PHP Performance: Identifying and Fixing BottlenecksMay 11, 2025 am 12:13 AMPHP performance bottlenecks can be solved through the following steps: 1) Use Xdebug or Blackfire for performance analysis to find out the problem; 2) Optimize database queries and use caches, such as APCu; 3) Use efficient functions such as array_filter to optimize array operations; 4) Configure OPcache for bytecode cache; 5) Optimize the front-end, such as reducing HTTP requests and optimizing pictures; 6) Continuously monitor and optimize performance. Through these methods, the performance of PHP applications can be significantly improved.
Dependency Injection for PHP: a quick summaryMay 11, 2025 am 12:09 AMDependencyInjection(DI)inPHPisadesignpatternthatmanagesandreducesclassdependencies,enhancingcodemodularity,testability,andmaintainability.Itallowspassingdependencieslikedatabaseconnectionstoclassesasparameters,facilitatingeasiertestingandscalability.
Increase PHP Performance: Caching Strategies & TechniquesMay 11, 2025 am 12:08 AMCachingimprovesPHPperformancebystoringresultsofcomputationsorqueriesforquickretrieval,reducingserverloadandenhancingresponsetimes.Effectivestrategiesinclude:1)Opcodecaching,whichstorescompiledPHPscriptsinmemorytoskipcompilation;2)DatacachingusingMemc
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
SublimeText3 Linux new version
SublimeText3 Linux latest version
Zend Studio 13.0.1
Powerful PHP integrated development environment
WebStorm Mac version
Useful JavaScript development tools
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.
Dreamweaver CS6
Visual web development tools
