MySQL? ?? ?? ??????
Aprimarykeyinmysqlisacolumnorsetofcolumns? chatiquelifieseachrow, inforcinguniquencesandprohibitingnullvalues; itmustbeunique, notnull, limitedtoonepertable (whitcanspanmultiplecolumns), andautomallasticalscratescreatescratescratescreatescratescratescrates
Aug 18, 2025 am 11:14 AM
MySQL? ?????? ??? ? ??????
NormalizationinMySQLisadatabasedesignprinciplethatorganizestablestoreduceredundancyandimprovedataintegritybyeliminatingduplicatedataandensuringproperdependencies.Itinvolvesdividinglargetablesintosmaller,relatedonesandlinkingthemthroughkeys,followinga
Aug 18, 2025 am 10:32 AM
MySQL?? ??????? ??? ??? ??????
MySQL ??????? ???? ?? MySQL-UuserName-P? ???? ??? ??? ? ?? CreateAbasedAbase_Name? ??????. createAbasemyApp_db? ?? ??????? ???? ??; ?? ?? ??? ???? createAbaseifnotexistsmyApp_db;? ??? ?? usemyapp_db;? ?? ??????? ??????.
Aug 18, 2025 am 10:02 AM
MySQL? ???? ??, ? ?? ?? ???? ??
Year () ??? ???? Selectyear ( '2025-04-05')? ?? ??? ???? 2025 ?? ?????. 2. Month () ??? ???? Month (1-12) ?? MonthName ()? ???? SelectMonth ( '2025-04-05')? ?? ? ??? ???? 4; 3. Day () ?? Dayofmonth ()? ???? ?? (1-31), dayofweek ()? ???? ? ? (1-7), DayName ()? ????? SelectDay ( '2025-04-05')? ?? ?? ?? ( '2025-04-05')? ?? ??? ?? ???? ?? NULL? ?????.
Aug 18, 2025 am 08:57 AM
MySQL? ????? ???? ???? ??
MySQL ????? ???? ????? select ?? ???????. ?? ??? selectColumn1, collect2fromtable_name???. 1. SelectName, ??? ??? ?? ?? ?? ?? ??? ? ? ??? ??????. 2. SelectFromusers? ??? ?? ???? ????????? ? ???? ???????. 3. Where ?? ???? SelectName, Agefromuserswhereage> 25? ?? ??? ????? =, in, like, mene etce ?? ?? ?? ???; 4. Orderby? ???? selectna? ?? ??? ??????.
Aug 18, 2025 am 08:42 AM
mysql?? find_in_set () ??? ??????
find_in_set ()? returns1ste1 ?? PropectringInacomma-separatedList, or0ifnotfound, andiSuseforearchingDenormalizedData; ??? ItRequireseXactMatches, iscase-insensitiveBefault, performorlyOnlargetablesDuetolackOfIndexUpport ? ShouldBeavoid
Aug 18, 2025 am 07:57 AM
MySQL?? ?? ???? ???? ??
MySQL?? ?? ???? ????? ?? ???? ???? ?? ??? ????? InnoDB ?? ??? ???????. 1. ???? ?? ? Point ? SRID4326? ?? ?? ??? ???? ?? ??? ????? ?? SpatialIndex? ??????. 2. Point, Linestring, Polygon ? ST_PointfromText? ?? ???? ???? OGC ?? ?? ??? ??? ???? ?? ? ??? ?? ?????? ?????. 3. ST_DISTANCE_SPHERE? ???? ?? ?? ?? (?? ??)? ????? ST_CONTAINS? ???? ???? ???? ??? ????? Orderby ??? ?? ?? ??? ??????. 3. ST_DISTANCE_SPHERE? ???? ?? ?? ?? (?? ??)? ????? ST_CONTAINS? ???? ???? ???? ??? ????? Orderby Disting? ??????.
Aug 18, 2025 am 07:35 AM
MySQL?? ??????? ???? ??? ??????
MySQL ??????? ????? DropDatabase ?? ??????. ? ??? ?????? ? ?? ???? ????? ???????? ???????. ?? ??? dropdatabasetest_db? ?? dropdatabasedatabase_name???. ??????? ????? ???? ?? ?? dropdatabaseifexistsold_project? ?? ??? ??? ?? dropdatabaseifexistsdatabase_name? ???????. ? ??? ??? ? ??? ?? ??? ?????. ???? ???? ?? ?????? ??? ???? ??? ???? ???? ?? ? ShowDataba? ???????.
Aug 18, 2025 am 07:06 AM
MySQL?? ??? ???? ??
MySQL? ?? ??? Date_format () ??? ?? ????, ?? ??? ???? ?? ?? ???? ??? ?????. ?? ??? date_format (??, ??)???. ???? ?? ??? ??? ????. %y (4 ?? ??), %m (2 ?? ?), %d (2 ?? ??), %m (?? ? ??), %b (?? ? ??), %h (24 ??), %i (?), %p (am/pm) ?; ?? ??, "2025-03-1514 : 35 : 45"~ "3 ? 15,2025"~ "%m%d,%y"? "%d-%"15-mar-202502 : 35pm "?? ?????.
Aug 18, 2025 am 06:25 AM
? ??? ????? MySQL ???
??? ???? ??, ??? ? ?? ??, ?? ?? ?? ?? ? ???? ????? ???? MySQL ?? ? ??? ??? ??? ?? ? ? ????. 1. ?? ??? ?? ??? ???? InnoDB? ?? ??? ?????. 2. ??? ??? ?? ??? ????? ????, ??? ??? ?? ??? ??? ???? ???? ????? ??????. 3. ?? ? ??, ?? ?? ?? ? ?? ??? ?? ?? ?? ?? ??; 4. ????? ??, ?? ?? ?? ? ?? ??? ???? ??? ?????? ??? ????? ??? ?????.
Aug 18, 2025 am 05:25 AM
MySQL? IP ??? ???? ???? ??
varbinary (16) ?? bigint? ???? IP ??? ??????. 1. IPv4?? inet_aton ()/inet_ntoa ()? ?? ??? ?? intunsigned? ??????. varbinary (16)? ???? inet6_aton ()/inet6_ntoa ()? ?? ?????. ?? ??? ???? ??? ??, 6. ?? ???? ?? ?? ???? ?? IP ??? ????? ???? ?? ? ??? ?????.
Aug 18, 2025 am 03:01 AM
MySQL?? ???? ???? ??
Orderby? ????? ?????? ?? ??? ?? ???? ? ???? ASC ?? DESC? ??? ? ????. 1. ?? ? ?? : ?? ??, OrderBysalaryDesc? ??? ?? ?????. 2. ?? ?? ?? : ?? ??, OrderByDepartmentAsc, SalaryDesc? ?? ??? ?? ??????, ??? ?? ?????. 3. ??? ?? : ?? ??, OrderBy2desc? ? ?? ?? ?? ?? ??? ????? ????. 4. Process NULL ? : NULL? ????? ?????? ? ?? ??? ??? OrderByCommissionInull ? CommissionASC? ???? ??? NULL? ?? ? ? ????. 5. ?? ???? ?? ??? ??? ??, Collate? ??? ???? ? ??? ? ????.
Aug 18, 2025 am 01:54 AM
mysql?? now ()? current_timestamp? ???? ??????
?? () ? current_timestamm ?? ???? ??? ??? ????? ? ???? ??? ? ?? ????? ?? Current_Timestamp ? ??? ? ??? Current_Timestamp? SQL ??? ???? ??? ??? ????? ?? _timestamp? ??? ??? ?? DDL?? ???????.
Aug 18, 2025 am 01:35 AM
MySQL?? JSON ???? ???? ??? ??????
MySQL? ???? JSON ???? ???? ??? ???????? ? ??? ? ???? ?? ??, ?? ? ?????. ?? 5.7??? JSON ??? ?????. ?? JSON ??? ??? ?? ???? ??? ? JSON ?? ???? MySQL? ??? ???? ?????. json_extract () ?? -> (returns quoted strings) ? ->> (? : profile- >> "$ .city"? ?? ?? ??? ???? ???? ???? ?? ??? ?? ? ????. ??? ?? JSON ?? ????? AddCityVarchar (50) ?? ?? ??? ????? ?? ?? ? ? ? ???? ???? ?? ????.
Aug 17, 2025 am 11:21 AM
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