MySQL?? ?? ?? ??? ???? ???? ??
MySQL? ?? ?? ??? ??? ????? st_distance_sphere () ??? ???? ??? ?? (?? ? ??)? ??? ??????. 1. ??? ?? ?? ?? ? ???? ??? srid4326? ?????. 2. ST_DISTANCE_SPHERE () ??? ???? ??? ??? ?? ???, ?? ??? ?????. 3. ??? ?? ???? ?? ???? ???? mbrwithin ()? ?? ?? ? ?? ?? ???? ???? ???? ???????. ?? ?? : selectId, name, st_distance_sphere (coord, point (40.7128, -74.0060)) asdistancefroml
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MySQL?? ?? ??? ???? ??
?? ??? ?? SQL ?? ?? ? ?? ?????, ????, ? ??? ??? ??? ? ????. 1. ???? ????? ??? ?? ?? ?? ?? ?? ??? ???? ???? ??? ? ??? ???? ?? ?? ??; ?? ?? ?? ???? ???? ?? ????, ????, ?? ???? ??? ? ????. 2. ??? ?? ??? ???? ?? ?? ???? ???? ?? ?? ??? ???????. 3. SELECT ?? ?? ??? ??? ?? ?? ????, ?? ?? ?? ?? ? ? ? ????? ??? ??? ? ? ????. 4. ?? ?? ??? ?? ??? ???? ? ?? ? ? ????, ?? ? ????? ??? ? ?? ???? ???????. ? ?? ??? ?? ?? ?? ?? ?? ??? ???? ?? ????.
Aug 14, 2025 am 11:54 AM
MySQL?? AVG ??? ???? ??
theavg () functionInMySqlisanAggregateFunctionEdTocalculateAverAverValueOfAnumericColumn.ITSECTSTATEMENTEDENTERMESTEMENDINGISTEMONDISTEMONDISTEMONDINGINGINGINGINGINGINGINGEDDATASUCHASOVERAGEPRICES, SCORES, SALARIES, ORANYMEASU
Aug 14, 2025 am 11:41 AM
MySQL? ????? ?? ?? ??? ???
MySQL ????? ?? ????? Altertable ?? DropColumn ?? ???????. ?? ??? AltertableTable_namedRopcolumncolumn_name???. ? ???? ?? ? ?? ????. ???? ?? ?? ????? ???????. ??? ??? ?? ?????, ??? ??? ?? ??? ? ????. ??? ??? ?? ? ? ????. ?? ??, ?? ?, ??? ?? ?? ???? ???? ?? ???????. ?? ?? ? ?? ??? ? ??? ? ?? ??? ???????. ?? ?? ???? ???? ?? ???? ????? ??? ???? ?? ??? ??? ???????.
Aug 14, 2025 am 10:56 AM
MySQL?? ?? ?? ???? ??
TOSETAPRIMARYKEYWHENDATIALATIAL, USETHEPRIMARYKYCOSTENTINTHECREATETEBSTATEMENT, SABLESDEFINITINSINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINGINIDINTAUTO_INCREMENTPRIMARYKEYORACOMPOSITEKEWITHKEY (COLUCT1, COLUMEN2) .2
Aug 13, 2025 pm 12:15 PM
MySQL ??????? ?? ??? ??????
themaximumsizeofamysqldatabaseisnotfixedandsonmultiplefactors, nodbsupportingupto644terabytespertableanddatabasesexeceed100 tbpossibleinpractice, whilemyiSamtablescanreachupto256terabytesbuteReliTedifileSteyfileSteyfileSteyfileSteMCOTSYFTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTERTENTLECFILETER
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?? ???? ??? Union? ???? ??
Union? ???? ?? ???? ??? ?? ? ? ? ?? ?? ? ?? ???? ?? ?? ??? ??? ??????????. ?? ??? ? ??? ? ?? ???? ????. Union? ???? ?? ?? ???? ???? Unionall? ?? ? (?? ??)? ???? ??? ?????. ??? ??? ??, OrderBy? ?? ?? ?? ?? ???????. ??? ??? ?? ?? ??? ??? ?? ? ? ????. ?? ? ?? ?? ?????? ???? ??? ?? ??? ??? ?? ??? ??????. ? ??? ???? ??, ?? ?? ??? ?? ?? ?? ??? ??? ???? ???? ?????.
Aug 13, 2025 am 11:54 AM
MySQL Enterprise Edition vs Community Edition ??
MySQLCommunityedition? ?? ??? ?? ????? ??? ?? ?? ?? ?????. EnterpriseEdition? ?? ??, ???? ? ?? ??? ???? ?? ?????. 1. EnterpriseEdition?? ?? ???? ?? (? : MySQlenterPrisemonitor), ??? ?? ?? (MySQLENTERPRISEBACKUP) ? ?? ?? (MySQLENTERPRISESECURITY)? ????? ?? ??? ??? ?? ??? ?????. 2. EnterpriseEdition? ?????? ?? ? ??? ???? ?????
Aug 13, 2025 am 10:10 AM
MySQL?? ?? ?? ?? ??? ??? ???? ??
useconditionalwhereclauseswithor? isnullto handleoptionalparametersbyingeachfiltertobeskipperameterisnull, ensuringsafeprepredstatementusage.2.builddynamicsqlinepplicationcodetoincludeonlytheprovidedFilters, ?? ? QuicingAndutilization
Aug 13, 2025 am 10:09 AM
MySQL ??? ?? ? ?? ??? ??
?? ???? MySQL? ???? ??? ???????, ?? ?? ?? ???? ???? ??? ?? ???? ???? ? ???? ??????? ??? ??? ??? ??? ?? ??? ???? ?? ?? ??? ?????????. ???? ??? ??? ????. 1. ? ??? ???? ? ??? ?????. 2. ?? ???? ???? ?? ??? ??????. 3.?? ???? ???? ? ??? ??????. 4. ??? ? ???? ???? ???? ?? ?? ? ?? ??? ??????. ??? ?? (Datad
Aug 13, 2025 am 09:09 AM
MySQL ??? ????? ???? ??? ???? ??
MySQL ??? ????? ???? ??? ????? ?? ??? ????? ????????. setglobalevent_scheduler = on? ???? ?? ? ????. ?? ?? ??? event_scheduler = on? ???? ?? ????. ?? ?? ?? ? ??? ? ? ?? ? ?? ?? ?? ??? ???? CreateeeTeeventXistSdaily_log_cleanuponschedulevery1dayStartStimestamp (Curdate () Interal1day, '00 : 00 : 00 :
Aug 13, 2025 am 07:12 AM
MySQL? ?? ???? ????? ???? ??? ??????
MySQL ?? ??? ???? ?? ?? My.cnf (Linux/MacOS) ?? My.ini (Windows)? ???? [MySQLD] ???? ?? = ? ?? ??? ??????. 2. ??? ?? ? ? MySQL ???? ?? ?????. Linux? sudosystemctlrestartmysql? ???? Windows? NetStopMySql ? NetStartMysql? ?????. 3. ??? sudonestat-tulnp | grepmysqld ?? mysql-uroot-p-p new port-host = 127.0.0.1? ?? ?????? ??????. 4. ???? ? ??? ??????
Aug 13, 2025 am 06:07 AM
MySQL?? ???? ???? ???? ??? ??????
analyzeandrepairtables? Queeriesslowdown, ?? ?? ?? ??, ?? ?? FormyIsamtables.2.runanalyzetableTupDateIndexStaticsandimproveQueryOptimizerDecisions, LockingTableBriefly.3.userePairtableTofixMcorruption, with with allorsindicatecorrastion, oraftercrashes, ?? formyisamtables.2
Aug 13, 2025 am 04:32 AM
MySQL?? ??? ???? ??
MySQL?? ????? ????? InnoDB? ?? ???? ?? ???? ??? ???????. 1. innodb : showreatetableyour_table_name? ????? ???? ??????. innodb? ?? ?? altertableyour_table_nameengine = innodb? ??????. 2. ??? ?? ??? ?????? : startTransaction? ????? ??????. 3. updateAccountssetBalance = balan ? updateAccountssetalance
Aug 13, 2025 am 03:26 AM
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