
SQL?? ????? ???? ??
AsqltransactionissinglolegicalUnitofwork that attensuresDataintegrityFollowingAcidPrinciples : ???, ???, ?? ? ???; 2.TransactionSArctionArecontrolledusingBegin (OrstartTransaction), CouternSeveChanges, AndrollbackToundothem;
Sep 04, 2025 am 07:09 AM
?? SQL? ?? ? ?? ? ?? ???? ??? ??????
?? ? ???? ?? ?????? ?????? ??? ?? ???? ???????. 1.mysql? ???? whereyour_columnregexp '^[0-9] $'; 2.postgresql? wheryour_column ~ '^[0-9] $'? ?????. 3.sqlserver? wheryour_columnnot like '%1%'andyour_columnisnollandyour_column '; 4.sqlite? ?? ? ?? ?? ?? ??? ?????? ?? ????. ? ??? ? ?? ?? ?? ? ???? ??? ?? ??? ???? ??? ? ?? ????????. 0-
Sep 04, 2025 am 04:45 AM
SQL?? AVG ??? ???? ??
TheavgFunctionInsqlCalculatesTheAverage? asshowninSelectAvg (column_name) fromTable_name; itignOresNullSbyDefault, canbegroupedwithpuputoryspercepperceppercepperorgespperorgespperorgessperationsperceptresspperorgestepperorgestperorgestperorgestperorgestperorgestperouse
Sep 04, 2025 am 04:26 AM
SQL?? ?? ??? ?? ?? ??? ??????
sqlserver? eomonth () ??? ?????. 2.mysql ? Oracle ?? Last_day () ??? ?????. 3.postgresql? date_trunc + ???? ?????. 4.sqlite? ?? ??? ???? ??? ??? ?????. ?? ??????? ?? ?? ??? ???? ?? ??? ?? ???? ?????.
Sep 04, 2025 am 02:27 AM
SQL? ???? ?? ???? ??? ???? ???? ??? ??????
CTE? ???? SQL ??? ???? ?? ??? ?? ?? ? ? ????. 1. ???? ????? ?? ??? ??? ??? ?? ??? ???? ?????. 2. ??? ???? ???? ?? Active_users ?? Top_Products? ?? ???? ??? ??????. 3. ?? CTE? ?? ??? ?? ??? ??????. ?? CTE? ?? CTE? ?? ?? ? ???; 4. ? CTE ?? ??? ???? ??? ??? ??? ?? ???, ?? ? ?? ??? ??????. 5. CTE? ?? ?? ?????? ???? ????? ? ???? ??? ??????? ?? ??? ? ?? ? ? ????. ????? SQL? ????? ??? ???? ????? ????.
Sep 04, 2025 am 12:51 AM
SQL? ???? ??? ???? ??
SQL? ???? ??? ????? ?????? ???? ?? ??? ???????. Selectyear ( '2025-04-05')? ?? MySQL, SQLServer ? MariaDB?? ?? () ??? ???? 2025 ?; PostgreSQL??? 2025 ?? SelectExtract (Yearfom'2025-04-05 ':: Date)? ?? ?? SQL? ??? (?? ...) ??? ???????. PostgreSQL? ?? date_part ( 'Year', Date)? ?????
Sep 03, 2025 am 07:23 AM
SQL? ?? ?? ?? ???? ???? ??? ??????
SQLServer?? ???? ?? ? ?? ?? ?? ??? ????? ?? SQL? ???????. ?? ??? ??? ????. 1. ?? ??? ?? ?? ? ?? ???? ???? ???? ??? ??? ? ??? ?????. 2. ?? ? ?? ???? ?? ? ??? ???? quotename ()? ???? ? ??? ???? ?????. 3. ?? ? ? ??? ?? ?? ???? ?? ????? execsp_executesql? ?????. 4. ?? ? SQL ?? print@sql? ?? ??? ? ? ????. ? ??? ??, ? ?? ??? ?? ???? ???? ? ??? ??? ?? ? ?? ??? ????? ????, ??? ?? ??? ??? ???? ??? ?? ?? ???? ?????.
Sep 03, 2025 am 05:47 AM
SQL? ???? ??? ???? ??
thextractedayfromadateinsql, useday () orextract (dayfrom ...)? ?? : mysqlsupportsbothday () andextract (), postgres qlandoracleSeextract (), sqlserverallowsday () OrdatePart (day, ...), andsqliteRequiresttrftime ( '%d', ...)
Sep 03, 2025 am 05:22 AM
SQL?? ? ???? ???? ??? ???? ??
? ???? ???? ??? ???? ??? ?????? ?? ???? ?? ????. mySQL??? CreateUser ??? ???? ???? ???? ??? ???? ?? ?? ??? ????? ????? ??????. PostgreSQL?? CreateUser ?? Createrole? ???? ???? ? ???? ??? Grant ?? ?? ??????, ??? ?? ???? ?? ????, ? ??? ????? ?? ?? ? ? ????. SQLServer?? ?? Createlogin? ???? ?? ?? ??? ??? ??? ?? CreateUser? ???? ???????? ?????? ???? ??? ??? ?? ?? ?? ?? ??? ?? ?? (? : ? : ? :)? ?? ??? ???????.
Sep 03, 2025 am 02:28 AM
SQL?? ??? ???? ??? ???? ??
USRety ... CatchBlockStotRaperRorsinStordProcedures
Sep 03, 2025 am 02:14 AM
SQL? ??? ?????? ??? ?? ??? ??????
mysql : selectDatabase (); returnsTheCurrentDataBasenameornUllifnoneisSelected.2.postgresql : selectCurrent_Database (); returnSthenameOfTheMurentyConnectedDatabase.3.sqlserver : selectDb_name (); ????? stelecurrent -sTABASENAME.4
Sep 03, 2025 am 01:57 AM
SQL?? ?? ?? ??? ???? ??
toanalyzeaqueryExecutionPlaneffectively, Operationlikescans? ???? revealshowthedatabasexecutesaquery, sequerationslikescans, ceps, andsorts, usetoolslikesqlservermanagementstudio, explicinpostgresql, orexplainplanoracletov viewestimatedorac
Sep 03, 2025 am 01:31 AM
SQL?? ?? ???? ???? ??
?? ???? ????? From Clause?? ?? ?? ??? ???? ?? ??? ???????. ?? ??, Innerjoin ?? Leftjoin? ?? ??? ?? ??? ???? 3 ? ??? ???? ???? ???? ? ??? ?? ??? ?? ??? ??? ??? ??? ??????. ??? ??? ??? ???? ???? ????? ????? ?? ??? ??? ??? ??????. ? ??? ?? ?? ??? ???? ?? ? ? ??? ??? ???? ?? ??? ??? ? ? ??? ??? ???? ?? ? ? ????.
Sep 03, 2025 am 01:23 AM
SQL?? ??? ???? ???? ??
themodulooperatorinsqlreturnstheremaindivisionandisuusedforfiltering, ???, ?? indistifyingpatternsinnumericdata; itissupportedacrossdatabases withvaryingsyntax - mysql, postgresql, sqlite ? andoracle (10g) usethe%merverator
Sep 02, 2025 am 08:22 AM
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