?? SQL? ???? ??
DynamicsQlallowsBuildingandExecutingsQlstatementSatruntime, ThissentialsibleWhengeComponentSliketableMenamesOrconditionSearUnkNownUntilexecution; itiscommonlyUsedInstoredProceduresforfectibleQueries, OptionalFilters, DDlStatements ? Dynamicordering; ins
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Node.js??? ??? Redis? ???? ???
installisclient likeioredisorredisvianpm, thenconnectTororedisinnode.js.2.beforequeryingdatabaseorapi, checkifdataexistSinredisusingget; iffound, returnCachedData.3.3.ifnotincache, fetchfromdatabase, fetchfromdatabase, storeinrediswithsexpiration, fretupda
Sep 16, 2025 am 12:34 AM
?? ?? ??? ?? MongoDB ?? ??? ??????
mongodb ?? ?? ?? ??? ???? ???? ?? ( "executionStats")? ??????. ??? TotalDocsexAmined? TotalDocSreturned?? ?? ??? ?? ?? ????. 2. CollScan? ?? ??? ??? ???? ???? ????????. 3. ?? ? ??? ?? ??? ?? ? ??? ???? ?? {status : 1, createat : -1}? ?? ?? ???? ?? ???????. 4. ExecutionTimemillis? 50-100ms? ????? ???? ???????? ?? ??? ???? ????. 5. Indexonly? ?? ??? ?? ??? ??????.
Sep 16, 2025 am 12:11 AM
MySQL?? ?? ???? ???? ??? ??????
MySQL ?? ???? ?? ???? ???? ??? ??? ?? ?? ??? ???? ? ?????. CreateTemporaryTable? ?? ???????. ? ???? ?? ???? ???? ?? ??? ??? ??? ?? ???? ??? ? ? ????. ???? ?? ? ? 100?? ? ?? ???? ?? ??, ?? ?? ?? ??. droptemporarytabl? ?? ??? ? ????
Sep 15, 2025 am 05:25 AM
MySQL?? ? ??? ???? ??? ??????
WindowFunctionsInMySqlenAbleCalculationsOVESTOFSROWSSLATECURNTERWITHOUTCURNTERWITHOUTCULLAPSINGTHETHOUTCOLLAPSINGTEM, RunningRanking, RunningTotals ? RunningToTals
Sep 15, 2025 am 04:52 AM
MySQL?? if () ??? ???? ???
??? MySQL? if () ??? SQL ???? ??? ??? ???? ? ???? ??? if (??, value_if_true, value_if_false)???. ??? ?? ?? ?? ???? ?? ???? ?? ??? ???? ?? ?? ?? ???? ?? ? ?? ???? ? ?????.
Sep 15, 2025 am 04:39 AM
SQL?? ?? ???? ?? ???? ??? ??????
?? ?? ???? ???? ?? ??? ?? ??? ???? ??? ?? ??? ?????? ???? ?? ????. 1. SQLServer?? ?? quotename ()? ?? ?? ? ? ?? ?? ?? ?? SQL? ??? ? ?? Pivot? ???? SP_ExecutesQL? ???? ?? ? ???? ?????. 2. MySQL?? Group_Concat? ???? ?? ?? ? ?? ???? ???? ?? ?? ?? ?? ??? ??????. 3. ?? ??? ??? ??? ?? ? ??? ???? ???? ?? ???? ????? ????? ??? ????? ?? ???? ??? ?? ?? ? ??? ????? ??????. ? ?? ? ??? ?????????
Sep 15, 2025 am 04:00 AM
MySQL ????? ???? ???? ??? ??????
todeleterecordsinmysql, usedeletefromtable_namewherecondition; ?? specify hereclausetoavoiduntendeddataloss, and testwithelectfirst.forallrows, deleteremovevutkeepsstructure, whiletruncateSpaster-increment.backupdataanduseTransact
Sep 15, 2025 am 03:34 AM
MongoDB?? ?? ???? ???? ??? ??? ???? ??
ChangestreamsInMongoDBenAblereal-timemonitoringofdatachangesacrosscollection, ??????, ??????, ordeployments, ?? ??? ?????. ?????
Sep 15, 2025 am 03:23 AM
MongoDB?? ?? ??? ????? ???? ??
? : ??? ?? ??? ??? ??? ???? ?? ?????. ?? ???? ??? ?? ????? ?????. ??? ? ??????? ?? ?? ?? ??? ?????. ??? ??? ?? ???? ???? ??????? ???? ?? ??? ????? ?? ??? ?? ??? ?? ??? ???? ??? ?? ?? ??? ???? ?? ?????????.
Sep 15, 2025 am 03:20 AM
MySQL ??????? ??? ?? ??? ??????
SQL Query information_schema? ???? MySQL ?????? ??? ?????. 1. ??? ?????? ??? ?????? : selecttable_schemaas'databaseName ', round (sum (data_length index_length)/1024/1024,2)'at 'size (mb)'frominformation_schema.tablestable_schema = 'your_database_name'groupbytable_schema; 2. ?? ?????? ??? ?????? : Selec
Sep 15, 2025 am 03:17 AM
Redis Performance Metrics? ?????? ??? ??????
startwithredisinfocommandandslowlogtomonitorkeymetrics likeshitrate, memoryusage ? commandlatency, expandtoexternaltoolsforcontinuousOversight.
Sep 15, 2025 am 03:16 AM
SQL?? ?? ?? ?? ???? ??? ??????
Innerjoincombinesrowsfrommultipletablesbasedonarelatedcolumn, returningonlymatchingrows.thesyntaxusonsonspecifythejoindition, suchaslinkingcustomersandordordersviacustomer_id.forexample, explice, customersandordersreturnsonlycustomers shoplaclacswithlatord
Sep 15, 2025 am 03:11 AM
SQL? ???? ?? ???? ???? ?? ?? ?? ??? ??????
Useleftjoinwithisnulltofindunmatchedrows : selecta.fromtableAteftJointableBbona.id = b.idwhereb.idisnull; 2. aandternatially, usenotexistsforcomplexConditions : selecta..fleaWherenotexists (selectAbleAwherEnotex.Id = a.id);
Sep 15, 2025 am 02:57 AM
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