Onetsetsani Umphumphu Wanu wa Deta
Malo osungirako zinthu, pamphweka ake, ndi mtundu wa deta womwe umagwiritsidwa ntchito ndi ndondomeko mu deta. Mtundu uwu wa deta ukhoza kukhala wojambulidwa (monga nambala kapena chingwe) kapena mtundu wachizolowezi umene umatanthawuza zovuta pa data.
Kulowa kwa Deta ndi Ma Domains
Mukalowetsa deta mu mawonekedwe a intaneti a mtundu uliwonse - kaya ndi dzina lanu ndi imelo, kapena ntchito yeniyeni - deta yanu imasungira zomwe mumapereka kumbuyo. Malo osungirako zinthu akuyang'ana zolemba zanu malinga ndi zifukwa zoyenera. Mwachitsanzo, ngati mutalowa zip code, deta ili kuyembekezera kupeza nambala zisanu, kapena zip code zonse za US: nambala zisanu zotsatiridwa ndi chiwonetsero, ndiyeno nambala zinayi. Ngati mutalowetsa dzina lanu mu zip code munda, deta yanuyo ingadandaule.
Ndi chifukwa chakuti deta ikuyesa kulowa kwanu motsutsana ndi mayina omwe amalembedwa ku zip code. Dera ndilo makamaka mtundu wa deta umene ungaphatikizepo zoletsedwa.
Kumvetsetsa Domain Domain
Kuti mumvetsetse malo ochezera adiresi, tiyeni tikambirane mbali zingapo za database:
- A database zolinga zimatanthauzira zigawo, zomwe zimatchedwanso columns kapena minda. Mwachitsanzo, ngati muli ndi tebulo "Zomwe Mumafuna Kugwira Ntchito," zikhoza kukhala ndi zizindikiro za FirstName, LastName, JobTitle, StreetAddress, City, State, ZipCode, PhoneNumber ndi Email.
- Chikhumbo chirichonse chiri ndi chidziwitso chomwe chimatanthawuza zoyenera. Izi zingaphatikizepo mtundu wake wa deta, kutalika, mfundo ndi zina.
Mwachitsanzo, mayina a ZipCode angatanthauzire mtundu wa deta, monga nambala, yomwe imatchedwa INT kapena INTEGER, malingana ndi deta. Kapena wogwiritsa ntchito deta akhoza kusankha kufotokozera izo m'malo mwa khalidwe, kawirikawiri amatchedwa CHAR. Chikhumbochi chikhoza kufotokozedwa mozama kuti chikhale ndi kutalika kwake, kapena ngati chopanda kanthu kapena chosadziwika chiloledwa.
Mukasonkhanitsa zinthu zonse zomwe zimatanthauzira dera, mumathera ndi mtundu wamtundu wokhazikika, womwe umatchedwanso "mtundu wosonyeza deta" kapena UDT.
About Domain Integrity
Makhalidwe ololedwa a chikhalidwe amapanga chida chokhulupirika , zomwe zimatsimikizira kuti deta yonse m'munda ili ndi zoyenera.
Ulamuliro wodziwika umatanthauzidwa ndi:
- Mtundu wa deta, monga integer, chikhalidwe kapena decimal
- Kutalika kotalika kwa deta
- Mtunduwu, kufotokoza malire apamwamba ndi apansi
- Zovuta zirizonse, kapena zolepheretsa pa zovomerezeka. Mwachitsanzo, chipangizo cha zip code za US chingagwiritse ntchito chikhombo chonse cha ZIP + 4 , kapena chikho chonse cha nambala zisanu ndi zinayi.
- Mtundu wa chithandizo cha NULL, kapena ngati chikhumbo chingakhale ndi mtengo wosadziwika, kapena NULL
- Mtengo wokhazikika, ngati ulipo
- Mtengo wamtunduwu, ngati ukuyenera (mwachitsanzo, dd / mm / yy kapena mm / dd / yyyy)
Kupanga Domain
Kwa ma database omwe amagwiritsa ntchito SQL (Structured Query Language) kapena kukoma kwa SQL, gwiritsani ntchito CREATE DOMAIN SQL lamulo.
Mwachitsanzo, mawu owonetsa apa amapanga chikhalidwe cha ZipCode cha mtundu wa data CHAR ndi zilembo zisanu. NULL, kapena mtengo wosadziwika, saloledwa. Zambiri za deta ziyenera kugwa pakati pa "00000" ndi "99999." zimapanga chikhalidwe cha ZipCode cha mtundu wa data CHAR ndi zilembo zisanu. NULL, kapena mtengo wosadziwika, saloledwa. Zambiri za deta ziyenera kugwa pakati pa "00000" ndi "99999."
LENGANI DOMAIN ZipCode CHAR (5) SANKHA NULL CHECK (VALUE> '00000' NDI VALUE
Mtundu uliwonse wa detawu umapereka njira yowonetsera malamulo ndi malamulo omwe amayendetsa deta yolandiridwa, ngakhale sichikutcha dzina lake. Onani zolemba zanu zachinsinsi kuti mudziwe zambiri.