Umsebenzi indalo etafileni SQL - Yenza Table

Ukusebenza zenkcazelo ezinxulumene ngqo iitafile inguqu kunye iinkcukacha ezikuyo. Kodwa phambi kokuqala yintshukumo kwetafile ukudala. Kukho umsebenzi SQL elikhethekileyo zokusebenzisa le nkqubo - "MASIDALE ITHEYIBHILE".

Into yokuqala!

Phambi kokuba bajongane inkqubo yokudala spreadsheets usebenzisa MS SQL "MASIDALE ULUHLU" umyalelo, kuyimfuneko ukuba ahlale phezu koko sifanele ukuba sazi phambi kokusebenzisa msebenzi.

Okokuqala, kufuneka beze igama kwetafile - kufuneka ibe yodwa kuthelekiswa kwabanye kwiziko ledatha, kwaye balandele imithetho embalwa. Igama kufuneka liqale nge leta (az), kwaye ke ngoko kungalandelwa nayiphi na oonobumba, amanani kunye underscore, ibinzana nto kufuneka ukuba igama Reserved. igama table ukudlula abalinganiswa-18.

Kokuba kuchaziwe igama, isakhiwo kufuneka ziphuhliswe: ukuza amagama kwiikholam Ndandikade ndicinga uhlobo idatha yazo, yaye eyiphi imihlaba kufuneka kuhluthiswa. Kukho kwakhona ngoko nangoko ukuqinisekisa intsimi lwangaphandle kunye nezitshixo zaseprayimari, kwaye kuyenzeka amaxabiso data ukunciphisa.

Ezinye i table kuba lula ngokufanelekileyo kujonge izinto ilungile, ngoko ke inyathelo yokudala itafile, zingakotshwa babecinga ukuba iphele.

syntax

Ubume be-iitafile, uyakwazi ukuqhubeka ukuba indalo yayo. Yenza kube lula ngokwaneleyo, esebenzisa umsebenzi SQL "MASIDALE ITHEYIBHILE". Ifuna umsebenzisi ukucacisa ngaphambili wenza igama letheyibhile lomhlathi uluhlu, ebalula ukuba uhlobo ngalunye kunye negama. Le kwezivakalisi ngolu hlobo lulandelayo:

Dala ITHEYIBHILE table_name
({Column_name datatype [engagqibekanga ibinzana] [column_constraint] ... | table_constraint}
[, {Column_name datatype [engagqibekanga ibinzana ] [column_constraint] ... | table_constraint}] ...)

Wempikiswano ezisetyenziswa iimpawu zoyilo zezi zilandelayo:

• table_name - igama letheyibhile
• column_name - a ligama lomhlathi
• uhlobo data esetyenziswa kule nkalo - datatype
• Default - ibinzana ezisetyenziswa kwikholam emiselweyo.

Kwakhona kuyenzeka ukuba asebenzise ngaphezulu umsebenzi iimpikiswano ezimbini:

• nezicwangciso zomhlathi - colum_constraint
• Useto itheyibhile - table_constraint

Kubo, umsebenzisi akanokukwazi ucacise umsebenzi ezifunekayo umda okanye iimeko yokuzalisa itafile.

Iimpawu ukudala iitafile

Xa ubhala umbuzo SQL "MASIDALE ULUHLU" function, kuyimfuneko amaxesha ukuseka imithetho nangokundizalisa emasimini. Ukuze wenze oku, kufuneka ukuba songeze iimpawu iimpawu ezizodwa ukuchaza iseti ethile kweemeko.

Ukuze ukucacisa ixabiso engenanto, uze ucacise igama nohlobo kumhlathi kufuneka abhalise omnye amagama angundoqo apho kubakho kwisisele: byte (inokuba amaxabiso null), okanye NOT byte (intsimi kufuneka igcwaliswe).

Xa ekudaleni itafile kwiimeko ezininzi kufuneka ukuba basebenze irekhodi nganye ukuze kukuphepha ezimbini twatse. Ukuze wenze oku badla ukusebenzisa amanani umgca. Ke kaloku, ukuze afune ulwazi umsebenzisi womba entsha, efumaneka itafile, kwi umsebenzi "MASIDALE ULUHLU" Kwanele ukucacisa ikholam iqhosha ngokubhala igama "isitshixo Primary" emva endle ahambelanayo. Kwiimeko ezininzi, oko ke iqhosha kwaye kukho unxibelelwano phakathi ezitafileni.

Ukuqinisekisa koqiniso enesitshixo Primary kusetyenziswa langaphandle iqhosha ipropati "iqhosha langaphandle". Esalatha umhlathi, le impahla ukwamkhulu ukuba lo mhlaba uya kuba ixabiso efanayo njengenye kwabo eziziiprayimari kwikholam isitshixo yezintlu efanayo okanye ezahlukeneyo. Ngaloo ndlela umntu uqinisekise ukuba idatha.

Ukubonelela ukuqinisekiswa lokuthobela kunye iseti ethile okanye inkcazelo, sebenzisa kweakhawunti ngemfanelo. Azimiselweyo i zamvanje uluhlu lweempikiswano kusetyenziso lwefowuni, uze ube parameter kwabantu a seBhulin. Yiyo, unganciphisa uluhlu lwamaxabiso kunokwenzeka, umzekelo, sebenzisa intsimi itafile "Gender" kuphela oonobumba "M" yaye "F".

Ngaphandle kwezo thaca, umsebenzi SQL "MASIDALE ULUHLU" iye iimpawu basebaninzi ezithile, kodwa asetyenziswe yokwenza azixhaphakanga.

izibonelo

Ukuze uqonde ngokupheleleyo esebenza ngayo umsebenzi, kubalulekile ingqalelo xa kusenziwa, indlela MASIDALE ISICWANGCISO (SQL). Umzekelo ngezantsi idala itafile thaca apha ngasezantsi:

Dala ITHEYIBHILE Custom
(ID Char (10) HAYI isitshixo byte Primary,
Custom_name Char (20)
Custom_address Char (30)
Custom_city Char (20)
Custom_Country Char (20)
ArcDate Char (20))

Njengoko ubona, emisela ukungabikho enexabiso kwelo gumbi lentolongo (byte) kunokwenzeka ukuba ishiyiwe, ekubeni isetyenziswa yi ngokungagqibekanga.