Pezani Zambiri Zowona Zowonongeka
Mawonedwe owona malo akuthandizani kuti muchepetse mosavuta zovuta za zochitika zomwe zimagwiritsidwa ntchito kwa omaliza komanso kuchepetsa luso lawo lofikira deta yomwe ili mumasamba a masitepe mwa kuchepetsa deta yoperekedwa kwa wosuta. Kwenikweni, malingaliro akugwiritsa ntchito zotsatira za funso lachinsinsi kuti afotokoze mwatsatanetsatane zomwe zili mu tebulo lachinsinsi lachinsinsi.
N'chifukwa Chiyani Mukugwiritsa Ntchito Maonekedwe?
Pali zifukwa zikuluzikulu ziwiri zomwe zimapatsa owerenga mwayi wopeza deta kupyolera mu malingaliro mmalo mowapereka mwachindunji ku matebulo a deta:
- Mawonekedwe amapereka chitetezo chophweka, chophwanyika . Mukhoza kugwiritsa ntchito malingaliro kuti muchepetse deta yomwe wothandizira amaloledwa kuwona mu tebulo. Mwachitsanzo, ngati muli ndi ogwira ntchito patebulo ndikufuna kupereka owerenga ena mwayi wopezeka kwa ogwira ntchito nthawi zonse, mukhoza kupanga malingaliro omwe ali ndi zolembedwazo. Izi ndi zosavuta kwambiri kuposa njira zina (kupanga ndi kusunga mthunzi wa mthunzi) ndikutsimikizira kukhulupirika kwa deta.
- Kuwona kumawongolera zochitika zomwe akugwiritsa ntchito . Mawonekedwe akubisa zinthu zovuta pa tebulo lanu lachinsinsi kuchokera kwa ogwiritsa ntchito pamapeto omwe safunikira kuwawona. Ngati wogwiritsa ntchito atumizira zomwe zili muwonekedwe, sawona mazenera a tebulo osasankhidwa ndiwoneka ndipo sangamvetse. Izi zimawateteza ku chisokonezo chomwe chimayambitsidwa ndi zipilala zosatchulidwa, zizindikiro zosadziwika ndi makibulo a tebulo .
Kupanga Chiwonetsero
Kupanga lingaliro ndi losavuta: mukungoyenera kupanga funso lomwe liri ndi zoletsedwa zomwe mukufuna kuzikakamiza ndikuyika mkati mwa lamulo la CREATE VIEW. Pano pali syntax:
LENGANI KUONA maonekedwe a AS
Mwachitsanzo, ngati mukufuna kupanga antchito a nthawi zonse ndikuwona momwe ndakambidwira m'gawo lapitalo, mungapereke lamulo ili:
LENGANI KUONA nthawi yonse AS
Sankhani woyamba_name, last_name, employee_id
KUchokera kwa antchito
PAMENE udindo = 'FT'
Kusintha Chiwonetsero
Kusintha zomwe zili muzithunzi zimagwiritsa ntchito syntax yomweyo monga kulenga kwawonekedwe, koma mumagwiritsa ntchito Lamulo la ALTER VIEW mmalo mwa lamulo la CREATE VIEW. Mwachitsanzo, ngati mukufuna kuwonjezera chilolezo ku mawonedwe a nthawi zonse omwe amawonjezera nambala ya foni ya wogwira ntchitoyo, mungapereke lamulo lotsatira:
ALTER VIEW nthawi zonse AS
SANKANI choyamba_name, last_name, employee_id, telefoni
KUchokera kwa antchito
PAMENE udindo = 'FT'
Kuchotsa Maonekedwe
Ndisavuta kuchotsa zithunzi kuchokera ku deta pogwiritsa ntchito lamulo la DROP VIEW. Mwachitsanzo, ngati mukufuna kuchotsa ogwira ntchito nthawi zonse, mungagwiritse ntchito lamulo ili:
DZIWANI KUwona nthawi yonse