mysql三表连接查询问题
三表左连接查询，为何会出现重复数据，有木有大神讲解一下原因啦啦啦啦！比如现在我单独查询有九条记录，但是还需要其他附属表的字段，结果连接查询出现重复数据，总数也是九条，这是神马情况啊？
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PHP Performance: is it possible to optimize the application?May 14, 2025 am 12:04 AMYes,optimizingaPHPapplicationispossibleandessential.1)ImplementcachingusingAPCutoreducedatabaseload.2)Optimizedatabaseswithindexing,efficientqueries,andconnectionpooling.3)Enhancecodewithbuilt-infunctions,avoidingglobalvariables,andusingopcodecaching
PHP Performance Optimization: The Ultimate GuideMay 14, 2025 am 12:02 AMThekeystrategiestosignificantlyboostPHPapplicationperformanceare:1)UseopcodecachinglikeOPcachetoreduceexecutiontime,2)Optimizedatabaseinteractionswithpreparedstatementsandproperindexing,3)ConfigurewebserverslikeNginxwithPHP-FPMforbetterperformance,4)
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PHP performance optimization strategies.May 13, 2025 am 12:06 AMPHPapplicationscanbeoptimizedforspeedandefficiencyby:1)enablingopcacheinphp.ini,2)usingpreparedstatementswithPDOfordatabasequeries,3)replacingloopswitharray_filterandarray_mapfordataprocessing,4)configuringNginxasareverseproxy,5)implementingcachingwi
PHP Email Validation: Ensuring Emails Are Sent CorrectlyMay 13, 2025 am 12:06 AMPHPemailvalidationinvolvesthreesteps:1)Formatvalidationusingregularexpressionstochecktheemailformat;2)DNSvalidationtoensurethedomainhasavalidMXrecord;3)SMTPvalidation,themostthoroughmethod,whichchecksifthemailboxexistsbyconnectingtotheSMTPserver.Impl
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