Ezimeni eziningi zekhompuyutha, ukuthola wonke amathebula anegama lekholomu elithile ku-Oracle SQL kuyinkinga evamile abathuthukisi abahlangabezana nayo. Kungase kwenzeke ngesikhathi sokulungisa iphutha, lapho uzama ukuthola ukuthi ucezu lwedatha luvelaphi, noma mhlawumbe ngesikhathi sokwenza kabusha ikhodi, noma lapho uzama ukuthola isibambo kusizindalwazi esisha.
Ku-Oracle SQL, lo msebenzi ungafezwa kalula kusetshenziswa ukubuka kwesichazamazwi sedatha, USER_TAB_COLUMNS. Lokhu kubuka kuqukethe ulwazi mayelana nawo wonke amakholomu kumathebula omsebenzisi. Ngakho-ke, ngokubuza lokhu kubuka, kufanele ukwazi ukuthola wonke amathebula anekholomu ethile.
Ikhodi engezansi ibonisa ukuthi ungawufeza kanjani lo msebenzi:
KHETHA igama_lethebula KUSUKA ku-user_tab_columns LAPHO column_name = 'COLUMN_NAME';
Kule khodi, shintsha okuthi 'COLUMN_NAME' ufake igama lekholomu oyifunayo. Umbuzo uzobuyisela amagama awo wonke amathebula aqukethe leyo kholomu.
Ukuqonda Ikhodi ye-Oracle SQL
Ikhodi ye-SQL eyethulwe isebenzisa isitatimende se-SELECT , esibhekwa njengesisekelo sanoma yimuphi umsebenzi we-SQL. Isitatimende se-SELECT sisetshenziselwa ukukhetha idatha kusuka kusizindalwazi nokubuyisa kuphela leyo datha ethile ehlangabezana nezindinganiso ezithile.
Kulesi simo, sisebenzisa isitatimende esithi KHETHA ukuze sikhiphe amagama ethebula ekubukeni kwe-USER_TAB_COLUMNS. Isigatshana esithi LAPHO sibe sesisetshenziswa ukukhawulela imiphumela yosesho kumathebula kuphela anegama lekholomu elishiwo.
KHETHA ithebula_igama
KUSUKA kumakholomu_wethebhu_yomsebenzisi
LAPHO ikholomu_name = 'COLUMN_NAME';
Le khodi iyalela i-SQL ukuthi ibuyise amagama awo wonke amathebula lapho i-'COLUMN_NAME' ifana negama lekholomu elishiwo.
Amandla we-USER_TAB_COLUMNS
Ukubuka kwe-Oracle USER_TAB_COLUMNS kunikeza ulwazi oluningi mayelana namathebula futhi kuyithuluzi elinamandla ezandleni zomthuthukisi we-SQL. Kungumbono kusizindalwazi se-Oracle esiphethwe ngumsebenzisi we-SYS. Umsebenzisi we-SYS ungumsebenzisi okhethekile kusizindalwazi se-Oracle onamalungelo onke.
Lokhu kubuka kunikeza zonke izinhlobo ezahlukene zolwazi mayelana nesakhiwo sethebula, njengegama lethebula, igama lekholomu, uhlobo lwedatha yekholomu, ukuthi ikholomu ingaba yize, kanye nezinye izici eziningi. Ukubuza lokhu kubuka kuvumela umthuthukisi ukuthi athole ukuqonda okungcono nokulawula kusizindalwazi.
Eminye Imisebenzi Ewusizo Ye-Oracle SQL
Ngale kokusebenzisa izigaba ze-SELECT kanye ne-WHERE, kuneminye imisebenzi ebalulekile ku-Oracle SQL engasiza abathuthukisi ukuthi basebenzise kahle izizinda zabo zedatha. Isibonelo, i-JOINS ivumela ukuhlanganiswa kwemigqa evela kumathebula amabili noma ngaphezulu ngokusekelwe kukholomu ehlobene phakathi kwawo. Igama elingukhiye elithi ORDER BY lisetshenziselwa ukuhlunga isethi yemiphumela ngokulandelana okukhuphukayo noma okuphansi.
Ngaphezu kwalokho, isitatimende se-GROUP BY sivame ukusetshenziswa nemisebenzi ehlanganisiwe (COUNT, MAX, MIN, SUM, AVG) ukuhlanganisa isethi yemiphumela ngekholomu eyodwa noma ngaphezulu. Futhi ekugcineni, omunye umsebenzi owusizo yi- DISTINCT , esetshenziselwa ukususa imigqa ephindaphindiwe kusethi yemiphumela. Idlula ekusizeni unjiniyela ukuthi alondoloze isizindalwazi kodwa inwebeka ekuhlinzekeni ngamathuluzi anamandla okuhlaziya idatha.
Khumbula, inhloso enkulu yalesi sihloko bekuwukugxila ekutholeni wonke amathebula anegama lekholomu ethile kusizindalwazi se-Oracle SQL kusetshenziswa umbuzo wesizindalwazi esigxilile, vele, kusekuningi ongakufunda!
