Ufuna iseluleko ngokusebenzisa uLimi Oluhlosiwe Lokufuna ? Lezi Zisisekelo ze-SQL FAQ zihlinzeka izimpendulo zemibuzo ebuzwa kakhulu mayelana neSQL kanye nolwazi olusetshenziswayo. Qinisekisa ukuthi ulandela izixhumanisi "Ulwazi Oluthe xaxa" ekupheleni kombuzo ngamunye ukuze uthole incazelo eningiliziwe kanye nezifundo!
01 kwezingu-10
Ngingayithola kanjani idatha kusuka ku-database esebenzisa i-SQL?
Umyalo wokukhetha uwumyalo ovame ukusetshenziswa kakhulu ku-SQL. Ivumela abasebenzisi be-database ukuthi bathole ulwazi oluthile abafisa kusuka ku-database yokusebenza. Okuningi "
02 kwezingu-10
Ngidala kanjani i-database entsha noma ithebula elisha le-database?
I-SQL inikeza i- CREATE DATABASE futhi Yakha imiyalo ye- TABLE ukwengeza ulwazi olusha namatafula, ngokulandelanayo ku-database yakho. Le miyalo inikeza i-syntax eguquguqukayo kakhulu ekuvumela ukudala amatafula kanye nolwazi oluhlangabezana nezidingo zakho zebhizinisi. Okuningi "
03 ka-10
Ngingayifaka kanjani idatha ku-database?
Umyalo we-INSERT ku-SQL usetshenziselwa ukwengeza amarekhodi etafuleni ekhona.
04 kwezingu-10
Ngisusa kanjani enye noma yonke ithebula le database?
Ngokuvamile, kuyadingeka ukususa ulwazi olungasasebenzi kusuka kumininingwane yokuxhumana. Ngenhlanhla, uLimi LokuQuquka Oluhlelekile lunikeza umyalo wokuTHELELA oguquguqukayo ongasetshenziselwa ukususa okunye noma lonke ulwazi olugcinwe ngaphakathi kwetafula. Okuningi "
05 ka-10
Iyini inani le-NULL?
I-NULL yinani elisetshenziselwa ukumelela ucezu lwazi olungaziwa. Ulwazi oluphathekayo luphatha amanani we-NULL ngendlela ekhethekile, kuye ngokuthi uhlobo luni olusetshenziselwa ngalo. Uma inani le-NULL livela njenge-operand kuya ku-AND, ukusebenza kwe-FALSE uma enye i-operand iFALSE (ayikho indlela le nkulumo ingaba yiqiniso nge-operator eyodwa ye-FALSE). Ngakolunye uhlangothi, umphumela yi-NULL (engaziwa) uma enye i-operand ingu-TRUE noma i-NULL (ngoba asikwazi ukutshela ukuthi umphumela uzoba yini.) Okuningi ยป
06 kwangu-10
Ngingahlanganisa kanjani idatha kusuka kumatafula amaningi e-database?
I-SQL iyajoyina izitatimende ikuvumela ukuba uhlanganise idatha kusuka kumatafula amabili noma ngaphezulu kwimiphumela yakho yombuzo. Funda ukuthi ungayisebenzisa kanjani lobu buchwepheshe obunamandla ukuze uphumelele imibuzo yakho yedatha.
07 kwangu-10
Ngingajoyina itafula ngokwakho?
Yebo! Ungasebenzisa ukuzijoyina ukuze wenze imibuzo ekhonjiwe ye-SQL ibe lula lapho imibuzo yangaphakathi neyaphandle ibhekisela ithebula elifanayo. Lawa majoyina akuvumela ukuba uthole amarekhodi ahlobene etafuleni elifanayo.
08 kwezingu-10
Ngingafingqa kanjani idatha equkethwe kuthebula lemininingwane?
I-SQL inikeza imisebenzi ehlanganisiwe ukusiza ngokufingqwa kwemithamo emikhulu yedatha. Umsebenzi we-SUM usetshenziswe esitatimendeni sokukhetha bese ubuyisa inani lochungechunge lwamagugu. Umsebenzi we-AVG usebenza ngendlela efanayo ukuze unikeze isilinganiso sembalo sochungechunge lwamagugu. I-SQL inikeza umsebenzi we-COUNT ukuthola inombolo yamarekhodi etafuleni ehlangabezana nezidingo ezinikeziwe. Umsebenzi we-MAX () ubuyisela inani elikhulu kunawo wonke ochungechungeni lwedatha ngenkathi umsebenzi we-MIN () ubuyisa inani elincane kakhulu.
09 kwezingu-10
Ngingazihlanganisa kanjani ukwaziswa okufingqiwe?
Ungasebenzisa imibuzo eyisisekelo ye-SQL ukuthola idatha kusuka kumininingwane kodwa lokhu ngokuvamile akuhlinzeki ngokuhlakanipha okwanele ukuhlangabezana nezidingo zebhizinisi. I-SQL iphinde inikeze ikhono lokuqoqa imiphumela yombuzo ngokusekelwe emikhwalweni yezinga le-irowu ukuze usebenzise imisebenzi ehlanganisiwe usebenzisa isigatshana se-GROUP BY. Okuningi "
10 kwangu-10
Ngingavimbela kanjani ukufinyelela kwedatha equkethwe kwisitatimende se-SQL?
Ulwazi lwe-SQL lunikezela abalawuli abanesimiso sokulawula ukufinyelela kokuhlanganyela. Kulesi sigaba, abalawuli bakhiqiza ama-akhawunti womsebenzisi kumsebenzisi ngamunye wesigcinalwazi bese abanika lowo msebenzisi ekwenzeni eyodwa noma ngaphezulu egciniwe yemininingwane echaza indlela umsebenzisi avunyelwe ukuba asebenze ngayo nedatha. Okokugcina, umqondisi unikeza izimvume ezithile endimeni ukuvumela amalungu ukuba enze izenzo ezifunayo. Abasebenzisi bayenqatshelwe noma yikuphi ukufinyelela abangazange banikwe ngokucacile. Okuningi "