MySQL?? ?? ??? ???? ??
MySQL? ?? ??? ?? 5.7 ????? ??? ? ??? ?? 8.0 ??? ???????. 1. showvaribles like'have_query_cache '? ?? ??? ???? query_cache_type, query_cache_size ?? ??????. ??; 2. Set Query_cache_type = on, query_cache_size = 256m, query_cache_limit = 2m, query_cache_min_res_unit = 512k my.cnf? ????? ??????. 3. showstatus? ?? ??
Aug 14, 2025 pm 03:31 PM
?? ??? MySQL ??? ?? ???? ??? ??????
useudosystemctlrestartmysqlorsudosystemctlrestartmysqldonmodernlinuxsystemswithsystemd.2.usesudoServicemysqlRestArtorSudoser vicemysqldrestartonolderlinuxsystems.3.usesudo/etc/init/init.d/mysqlrestartfordirectscriptscriptscriptrestarts.4.onmacoswithhomebrew, ??
Aug 14, 2025 pm 03:27 PM
MySQL ?? ??? ???? ??? ???? ??
ToExecuteActiplefilefromthemySqlCommand-line, usethesourcecommandor \ .shortcutwithInmysql, orrunitfromtheoscommandline.1.usesour ce/path/to/script.sql; inmysqlafterlogginginandectingthedatabaseifneed.2
Aug 14, 2025 pm 02:44 PM
MySQL ?? ?? AWS S3 ?? Google ???? ????
MySQL? ??? AWSS3 ?? GOOGLECLOUDSTORAGE? ?????? ?? ????? ???? ??? ????? CRON?? ????? ??? ??? ???????. 1. ?? ??? ???? ?? ?????? ?? ?? ? ?? ???? ?? ? MySqlDump ????? ????. 2. AWSCLI ?? GSUTIL ??? ???? ??? S3 ?? GCS? ???????. 3. ?? ?? 2?? CRON ??? ??? ?? ????? ???? ???? ??? ?????. 4. ???? ??? ???? ?? 7 ? ?? ??? ??? ????? ????? ?? ??? ??????. ?? ????? ???? ???? ????? ?? ????????.
Aug 14, 2025 pm 02:11 PM
MySQL ??? ?? ?? ?? ??
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Aug 14, 2025 pm 02:03 PM
MySQL ????? ?? ?? ?? ??? ??????
tofindDuplicatesInasInasingLecolumnikeEmail, useGroupByWithHavingCount ()> 1ToshOwValuesAppeAringMoreThanOnce.2.fordUplicatesAcrossMultipleColumnsSsuchasfirst_nameAndllast_name, applyGroupByOnTheCombinedColumnsWithHavingCount ()
Aug 14, 2025 pm 02:02 PM
MySQL? ?? ???? ??? ??????
InnoDB? MySQL ?? ?? ???? ????, ?? ??? ? ??? ???? ??? ??????? ???? ? ?? ??, ?? ? ? ?? ??? ?????. MyISAM? ?? ??? ? ? ???? ????? ????? ? ?? ???? ????. ??? ??? ???? ?? ??? ??? ???? ??? ? ???? ????. CSV? ??? ??? ???? ????? ?? ?? ???? ?????. Blackhole? ??? ? ??? ???? NDB? ? ??? ???? ??? ???? Federated? ?? ???? ????? ? ???? Merge? ? ?? ???? ?? Myisam ?? ?????. ?? ??? ?? ?? ??? ?????????. InnoDB? ???? ?? ?? ????? ?????.
Aug 14, 2025 pm 01:47 PM
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
Aug 14, 2025 pm 12:22 PM
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
Aug 13, 2025 pm 12:11 PM
?? ???? ??? Union? ???? ??
Union? ???? ?? ???? ??? ?? ? ? ? ?? ?? ? ?? ???? ?? ?? ??? ??? ??????????. ?? ??? ? ??? ? ?? ???? ????. Union? ???? ?? ?? ???? ???? Unionall? ?? ? (?? ??)? ???? ??? ?????. ??? ??? ??, OrderBy? ?? ?? ?? ?? ???????. ??? ??? ?? ?? ??? ??? ?? ? ? ????. ?? ? ?? ?? ?????? ???? ??? ?? ??? ??? ?? ??? ??????. ? ??? ???? ??, ?? ?? ??? ?? ?? ?? ??? ??? ???? ???? ?????.
Aug 13, 2025 am 11:54 AM
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