Ukudala ukulandelana kuyisici esibalulekile se-Oracle SQL. Ukulandelana kuyizinto zesizindalwazi lapho abasebenzisi abaningi bengenza khona izinombolo ezihlukile. Kungenzeka ukuchaza izici ezithile ezifana nenani lokuqala ongaqala ngalo, usayizi wokukhuphuka, kanye nomkhawulo omkhulu, phakathi kokunye. Izinombolo ezikhiqizwa ukulandelana zingasetshenziselwa izinjongo ezimbalwa ezifana nokukhiqiza izihlonzi ezihlukile, okhiye abayinhloko, izinombolo zokulawula, nokunye okuningi.
Kuyini Ukulandelana ku-Oracle SQL?
Ukulandelana ku I-Oracle SQL kuyinto yesizindalwazi esikuvumela ukuthi ukhiqize amanani ezinombolo ezihlukile. Lokhu kuba usizo ngokuphawulekayo uma udinga ukwakha inani eliyingqayizivele lokhiye oyinhloko, noma noma yiliphi inani eliyingqayizivele ngaphakathi kwesizindalwazi. Isebenza kahle futhi ifaneleka njengoba ivimbela izinkinga ze-concurrency, inciphisa ithrafikhi yenethiwekhi, futhi igwema izindleko eziphezulu zokugcina indlela yokwabiwa esekelwe kumsebenzi.
DALA UKULANDELANA kwe-seq_name
QALA NGOKUQALA_i-value
UKWAMUKELWA NGE-increment_value
MAXVALUE inani_eliphezulu
Ukudala Ukulandelana
Ukuze udale ukulandelana ku-Oracle, ungasebenzisa isitatimende se-CREATE SEQUENCE. Ijeneretha yokulandelana iqala ngevelu yokuqala, inyuka ngenani elithile, futhi ayilokothi idlule inani eliphakeme. Uma kungekho mingcele echaziwe, amanani azenzakalelayo asetshenziswa. Ukulandelana kungase kukhule noma kunciphe, kuye ngokuthanda kwakho.
DALA OKULANDELAYO test_seq
QALA NGO-1
UKUNYUKA NGO-1
MAXVALUE 10000
Ikhodi engenhla izodala ukulandelana okuqanjwe ngokuthi 'test_seq'. Ukulandelana kuzoqala ku-1, kukhushulwe ngo-1 kunani ngalinye elilandelayo, futhi ngeke kudlule inani eliphakeme elingu-10000.
Ukusebenzisa Ukulandelana Okudaliwe
Ukuze usebenzise ukulandelana okudaliwe, ushayela umsebenzi we-NEXTVAL entweni yokulandelana ekhulisa ukulandelana futhi ibuyisele inani elisha. Umsebenzi we-CURRVAL ungasetshenziswa ukubuyisa inani lamanje lokulandelana ngaphandle kokulinyusa. Nokho, i-CURRVAL ayikwazi ukuthunyelwa ngaphambi kokuthi kubizwe i-NEXTVAL ngesikhathi.
FAKA KU-test_table (id, idatha) VALUES (test_seq.NEXTVAL, 'enye idatha');
Ukulungisa Nokususa Ukulandelana
Ukulandelana okukhona kungashintshwa kusetshenziswa umyalo othi ALTER SEQUENCE lapho umuntu engashintsha khona amapharamitha afana ne-INCREMENT, MAXVALUE, MINVALUE njll. Uma uchungechunge ludinga ukususwa, kusetshenziswa umyalo othi DROP SEQUENCE.
Shintsha ukulandelana:
ALTER SEQUENCE test_seq
UKUNYUKA NGO-2
MAXVALUE 50000
Lahla ukulandelana:
DREP SEQUENCE test_seq
Sengiphetha, ukulandelana kokuthi I-Oracle SQL nikeza ithuluzi elinamandla lokukhiqiza izinombolo ezihlukile, okhiye abayinhloko, namanye amanani endaweni enabasebenzisi abaningi. Kulula ukuzisebenzisa, ziyalungiseka, futhi ziyasebenza ngenxa yemvelo yazo ezimele engadingi izilawuli zokwenziwayo.