在MySQL5.5里,规范了sql语句表连接的写法。deleteusera,user2bfromuserajoinuser2bona.id=b.id;这样写在MySQL5.1里,可以正常执行,..
在MySQL5.5里,规范了sql语句表连接的写法。
这样写在MySQL5.1里,香港服务器,可以正常执行,但在MySQL5.5里就报错,下面是一个测试:
可以看到,执行时报错。那么规范后的写法是:
参考手册:
本文出自 “贺春旸的技术专栏” 博客,网站空间,香港服务器,请务必保留此出处

TodropaviewinMySQL,use"DROPVIEWIFEXISTSview_name;"andtomodifyaview,use"CREATEORREPLACEVIEWview_nameASSELECT...".Whendroppingaview,considerdependenciesanduse"SHOWCREATEVIEWview_name;"tounderstanditsstructure.Whenmodifying

MySQLViewscaneffectivelyutilizedesignpatternslikeAdapter,Decorator,Factory,andObserver.1)AdapterPatternadaptsdatafromdifferenttablesintoaunifiedview.2)DecoratorPatternenhancesdatawithcalculatedfields.3)FactoryPatterncreatesviewsthatproducedifferentda

ViewsinMySQLarebeneficialforsimplifyingcomplexqueries,enhancingsecurity,ensuringdataconsistency,andoptimizingperformance.1)Theysimplifycomplexqueriesbyencapsulatingthemintoreusableviews.2)Viewsenhancesecuritybycontrollingdataaccess.3)Theyensuredataco

TocreateasimpleviewinMySQL,usetheCREATEVIEWstatement.1)DefinetheviewwithCREATEVIEWview_nameAS.2)SpecifytheSELECTstatementtoretrievedesireddata.3)Usetheviewlikeatableforqueries.Viewssimplifydataaccessandenhancesecurity,butconsiderperformance,updatabil

TocreateusersinMySQL,usetheCREATEUSERstatement.1)Foralocaluser:CREATEUSER'localuser'@'localhost'IDENTIFIEDBY'securepassword';2)Foraremoteuser:CREATEUSER'remoteuser'@'%'IDENTIFIEDBY'strongpassword';3)Forauserwithaspecifichost:CREATEUSER'specificuser'@

MySQLviewshavelimitations:1)Theydon'tsupportallSQLoperations,restrictingdatamanipulationthroughviewswithjoinsorsubqueries.2)Theycanimpactperformance,especiallywithcomplexqueriesorlargedatasets.3)Viewsdon'tstoredata,potentiallyleadingtooutdatedinforma

ProperusermanagementinMySQLiscrucialforenhancingsecurityandensuringefficientdatabaseoperation.1)UseCREATEUSERtoaddusers,specifyingconnectionsourcewith@'localhost'or@'%'.2)GrantspecificprivilegeswithGRANT,usingleastprivilegeprincipletominimizerisks.3)

MySQLdoesn'timposeahardlimitontriggers,butpracticalfactorsdeterminetheireffectiveuse:1)Serverconfigurationimpactstriggermanagement;2)Complextriggersincreasesystemload;3)Largertablesslowtriggerperformance;4)Highconcurrencycancausetriggercontention;5)M


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

Atom editor mac version download
The most popular open source editor

Dreamweaver Mac version
Visual web development tools

SublimeText3 Chinese version
Chinese version, very easy to use

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

SublimeText3 English version
Recommended: Win version, supports code prompts!
