MySQL?? ?? ??? ???? ??
curtime () returnsthecurrenttimeinhh : mm : ssformatwithoutThedate; 1.useSelectCurtime () TOGETECURRENTSYSTEMTIME; 2. includePrecisionArgumentlikeCurtime (3) ForfractionEcondSuptomicroseconds; 3.insertcurtimecolecolecolecolecolecolecolecodecolecordecodecodecordecordecodecordecord.;
Sep 04, 2025 am 06:51 AM
MySQL?? NULL ?? ???? ??? ??????
useNullOrisnultNullTocheckFornUllValuesBECAUSESTANDARDERCOMPARISONSWITH = ??! = ret???
Sep 04, 2025 am 06:47 AM
MySQL?? ???? ??? ??
MySQL ???? ?? ???? ?? ??? ??? ???? ????? CreateUser? ???? ??? ??, ??? ? ????? ??? ?? Grant ?? ?? ?? ??? ???? ????? FlushPrivileges? ???? ?????. MySQL : MySQL-Uroot-P; 2. ??? ??? : CreateUser'Username '@'host'IndifiedBy'Password '; 3. ??? ?? : grantprivilege_typeondatabase_name.table_nameto'username'@'host '; 4. ??? ?? : ??
Sep 04, 2025 am 02:42 AM
MySQL?? ??????? ???? ??
USETHEUSEDATABASE_NAME; COMMANDABASE_NAME, COMMANDECTADATABASEINMYSQL, ?? DATABASE_NAMEWITHTHEDERDEDDATABASE.2.listAvailableABaseSwithShowDatabaseSHOWDATABASES.3
Sep 04, 2025 am 12:06 AM
MySQL?? ???? ??? ?? ???? ???? ??
TOCONVERTRINGTOUPPERCAYORLOWERCASEINMYSQL, USETHEUPPER () andLOWER () functions.1.USEUPPER (str) TOCONVERTRINGTOUPPERCASE (? : SELECTUPPER ( 'hellowORLD') returnShellowld, OrApplyIttoOlumnLikeSelectUpper (OrapPlyIttoOlumnlikeSelectupper)
Sep 03, 2025 am 07:01 AM
MySQL? ??? ??? ??? ??????
OptimizetableIsusedToreOrganizephysicalStorageAndeAmunuedSpacate ateRlaGedELETIONSORUPDATES, ?? ininnodbandmyisAmtables; itrebuildSthetableByCopyingAnlylaTATA, DEFRAGSTORAGE, ???? indexStatics, reseto-incrementcountersomeca
Sep 03, 2025 am 05:54 AM
??? ?? MySQL ?? ??? ????? ??
setInnodb_buffer_pool_sizeto70–80-80%ofram (? : 12Gon16gbram) ? ConconfigureInnodb_buffer_pool_instancesto1per1gbofbufferpool (? :, 8FOR12G); repykey_buffer_sizesmall (32–64m)? myiSamheavily? ???? ?? ?;
Sep 03, 2025 am 05:04 AM
MySQL?? ?? ??? ??? (CTE)? ???? ??
ActeIsDefinedUsingTheWithClauseandactSASATEMPORRESULTSETSTEFORASINGSETSETSTEFORASINGSTINGSTINGSTINGSTINGSTINGSTIMPOREARDERESTEFORASINGSOLEGELITERATERATINSLIKEAVERAGESALARY.3
Sep 03, 2025 am 04:15 AM
CSV ??? MySQL? ?? ?? ??
LoadDatainFile? ???? ?? CSV ??? MySQL? ?? ?? ?? ?? ?????. 1. CSV ??? ???? ???? MySQL ??? ??? ??? ????? ?? ??? ????? ??????. 2. CSV ??? ???? MySQL?? ???? ????. 3. LoadDatainFile ??? ???? ??? ???, ??? ? ? ??? ???? ??? ?? Local_Infile? ???????. 4. ??? ?? ? ?? LoadDataloCalInfile? ??????. ??, ??? ?? ??? phpmyadmin? ?? ?? ? ? ????. ?? ??, ?? ??, ??? ??, ?? ??? ? ?? ?????? ??? ???? ??? ??????.
Sep 03, 2025 am 04:11 AM
MySQL?? ???? ???? ???
?? ??? ??? ??? ???? ??? ??? ???? MySQL?? ?? ??? ????? ?????. ?? ???? ??? ????? : ?? ??? ??? ???? ?? ?? ??? ?? ??? ???, ?? ?? ??? UTC? ????, ?? ?? ?? ??? ???, mysql_tzinfo_to_sql? ?? ??? ????????, ?? ? ?? ??? ???? ?? ??? ??? ?? ??? ????????, ??? ??? ?? ?? ??? ???? ????, ???? ????, ??? ?? ??? ????, ??? ??? ??, ?? stimest ???? ???? ??? ?????. ??? ???? ???? ????? ?? ??? ?? ??????? ???? ?????.
Sep 03, 2025 am 02:09 AM
MySQL (Upsert)? ???? ??? ???? ??
???? ?? insertignoretoinsertarowonlyifitdoes? ???? ??, ??? skippingduplicatesbasedonauniqueconstraint; 2.useinsert ... onduplicatekeyupdateTupsert, insertingifnotexistsorupdatingifitdoes;
Sep 03, 2025 am 12:47 AM
MySQL?? ?? ?? ??? ??? ???? ??
?? ?? ??? ??? ????? ?? ?? ??? ??? ?? ? ?? InbooleanMode ? ?? ???? ?? ()? ?? match ()? ???????. 1. ?? ?? ?? FullText ???? ?????? ??????. ?? ? ?? CreateTable? ?? ??? ? ????. 2. match () ...? ?? ( 'Searchterms'InbooleanMode) ??? ???? ??? ?????. 3. ?? (??), - (??), "(??? ??), * (??? ??? ??), () (??), ~ (???? ???) ? ?? ???? ??? ???? ?? ? ? ???;
Sep 03, 2025 am 12:26 AM
MySQL?? ?? ??? ??? ?? ??? ??????
?? ??? ??? ???? ???? ???? ??? ??? ??? ???? ??? now () ??? ???????. ?? ?? ???? ??? ?? ???? ?? sysdate ()? ??????. ?? ? ??? ? Curdate ()? ???? ??? ??? ?? curtime ()? ??????. ??? ??? CreateTableLogs (idintprimarykey, messagetext, create_atdateTimedefaultNow ())? ?? ???? ??, ?? ?? ???? ? ??? ? ????.
Sep 02, 2025 am 08:27 AM
MySQL?? ?? ???? ?? ? ??? ?? ??
inanadjacencyListModel, LeaMnodesArefoundUsingAnteAteFoundUsingAlfeTeAteFoundEfoundeAntifynodeswithOutChildren : selectT1.id, t1.namefromtreet1leftjointreet2ont1.id = t2.parent_idwheret2.parent_idisnull; 2. inanestedsearedifiendifiedwherergt 1 : LeaMnodeRergt
Sep 02, 2025 am 07:51 AM
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