Ukukhangela iingcebiso ngokusebenzisa uLwimi loCwangciso oluHlangeneyo ? Ezi nkcukacha ze-SQL FAQ zibonelela izimpendulo kwimibuzo efunwa ngokuphindaphindiweyo malunga neSQL kunye neenkcukacha zolwazi. Qinisekisa ukuba ulandelelwano lwe "Info More" ekupheleni kombuzo ngamnye ukuze ufumane inkcazo ecacileyo kunye nezifundo!
01 ngo-10
Ndingayifumana njani idatha evela kwiziko ledatha usebenzisa i-SQL?
Umyalelo we-SELECT ngumyalelo oqhelekileyo osetyenziswayo kwi-SQL. Ivumela abasebenzisi beenkcukacha ukuba bafumane ulwazi oluthile abanqwenela kwi-database yolwazi. Kaninzi "
02 ngo 10
Ndidala njani i-database entsha okanye itafile entsha yedatha?
I-SQL inikeza i- CREATE DATABASE kunye ne-CREATE TABLE imiyalelo yokongeza ulwazi olutsha kunye neetafile, ngokulandelanayo kwi-database yakho. Le miyalelo inikeza i-syntax eguquguqukayo evumela ukuba wenze amatafula kunye neenkcukacha zolwazi ezihlangabezana neemfuno zakho zoshishino. Kaninzi "
03 ngo 10
Ndingayongeza njani idatha kwi database?
Umyalelo we-INSERT kwi-SQL isetyenziswe ukwengeza iirekhodi kwietafile ezikhoyo.
04 we-10
Ndingayicima njani enye okanye yonke itafile yedatha?
Ngokuqhelekileyo, kuyimfuneko ukususa ulwazi olungapheliyo kwi-database yolwazi. Ngethamsanqa, uLwimi oluCwangcisiweyo lweeNgxelo luhlinzekela umyalelo okhutshwayo okhutshwayo ongasetyenziswa ukususa ezinye okanye zonke iinkcukacha ezigcinwe ngaphakathi kwetafile. Kaninzi "
05 we-10
Yintoni ixabiso le-NULL?
I-NULL yixabiso elisetyenziselwa ukumela into engaziwayo yedatha. Iingqinisiso ziphatha ixabiso le-NULL ngendlela ekhethekileyo, kuxhomekeke kuhlobo losebenziso olusetyenziswa kuyo. Xa inani le- NULL livela njenge-operand kwi-AND operation, ixabiso le-operation li-FALSE ukuba enye i-operand iFALSE (akukho ndlela ibinzana lingaba yinyaniso kunye nomsebenzi omnye we-FALSE). Ngakolunye uhlangothi, umphumo yi-NULL (engaziwa) ukuba enye enye i-operand iyinyaniso okanye i-NULL (kuba asinakukwazi ukuba yintoni umphumo uya kuba.) Okunye ยป
06 ngo 10
Ndinokudibanisa njani idatha evela kwiithebula zeenkcukacha ezininzi?
I-SQL ijoyina izitatimende ikuvumela ukuba udibanise idatha kwiibhile ezimbini okanye ngaphezulu kwimiphumo yakho yombuzo. Funda indlela yokuphucula le teknoloji enamandla ukuze uphumelele imibuzo yakho yeenkcukacha zeenkcukacha.
07 ngo 10
Ngaba ndinokuzibandakanya netafile?
Ewe! Ungasebenzisa ukuzibandakanya ukuze ululaze imibuzo ephakamileyo ye-SQL apho imibuzo yangaphakathi neyiyo ibhekisela kwitheyibhile efanayo. Ezi zinto zivumela ukuba ufumane amarekhodi anxulumene netafile enye.
08 ngo 10
Ndingayifingqa njani idatha equkethwe kwitheyibhile yedatha?
I-SQL inikezela ngemisebenzi ebanzi ukuncedisa ngokushwankathela kwemimandla emikhulu yedatha. Umsebenzi we-SUM usetyenziswe kwisitatimende SOKUKHETHA kwaye ubuyisela inani leetekethi. Umsebenzi we-AVG usebenza ngendlela efanayo ukubonelela umyinge wemathematika woluhlu lwamanani. I-SQL inikezela umsebenzi we-COUNT ukufumana inani lamarekhodi etafileni ehlangabezana neemfuno ezinikezelweyo. Umsebenzi we-MAX () ubuyisela ixabiso elikhulu kwinani lwedatha elinikeziweyo ngelixa umsebenzi we-MIN () ubuyisela ixabiso elincinci.
09 we-10
Ndingayinceda njani iqela lushwankathelo?
Ungasebenzisa imibuzo eyisiseko ye-SQL ukufumana idatha esuka kwisiseko sedatha kodwa oku kaninzi akuboneleli ngeenkcukacha ezaneleyo zokuhlangabezana neemfuno zoshishino. I-SQL ikwabonelela ngekhono lokuqhelanisa iziphumo zombuzo ngokusekelwe kwiimpawu zamanqanaba emigangatho ukwenzela ukuba isebenze imisebenzi esebenzayo usebenzisa igatya le-GROUP BY. Kaninzi "
10 kwi-10
Ndingayinqanda njani ukufikelela kwedata equkethwe kwisiseko seSQL?
I-SQL yolwazi inikezela abalawuli abaneenkqubo zenkqubo yokulawula ukufikelela. Kule schema, abalawuli benze i-akhawunti yomsebenzisi ngamnye kumsebenzisi ngamnye wesiseko sedatha kwaye ke wabela loo msebenzisi kwiindima ezixhomekeke kumgca weenkcukacha ezichaza indlela umsebenzisi avunyelwe ukuba asebenze ngayo kunye nedatha. Ekugqibeleni, umlawuli unikela iimvume ezithile kwiindima zokuvumela amalungu athathe inxaxheba ukuba enze izinto ezifunwayo. Abasebenzisi bayayiphika naliphi na ufikelelo olungabonwanga ngokucacileyo. Kaninzi "