Isingeniso kubudlelwane beDatabase

Igama le-database elithi "ubudlelwane" noma "ubudlelwano" luchaza indlela idatha etafuleni exhunywe ngayo.

Abafika kumhlaba we-yolwazi bahlale benzima ukubona umehluko phakathi kwedatha kanye nespredishithi. Bona amatafula wedatha futhi baqaphele ukuthi imininingwane yolwazi ikuvumela ukuba uhlele futhi uphenye idatha ngezindlela ezintsha, kodwa uhluleka ukuqonda ukubaluleka kobudlelwane phakathi kwedatha enikeza ubuchwepheshe bokuxhumana bobudlelwano bobuchwepheshe igama layo.

Ubudlelwane buvumela ukuba uchaze ukuxhumana phakathi kwamatafula ehlukene e-database ngezindlela ezinamandla. Lezi zinsuku zingahle zenzeke ukuze zenze imibuzo enamandla ye-cross-table, eyaziwa njengejoyina.

Izinhlobo zeDatabase Ubudlelwano

Kunezinhlobo ezintathu ezihlukene zobudlelwane be-database, ngamunye obizwa ngezinga lezinhlu zamatafula ezingase zihileleke ebuhlotsheni. Ngayinye yalezi zinhlobo ezintathu zobuhlobo zikhona phakathi kwamatafula amabili.

• Ubuhlobo obunye kuya komunye buba khona lapho ukufaka ngamunye etafuleni lokuqala kunomunye, futhi kuphela, umlingani etafuleni lesibili. Ubuhlobo obunye nomunye abuvami ukusetshenziselwa ngoba kuvame ukuphumelela kakhulu ukubeka yonke imininingwane etafuleni elilodwa. Abanye abaklami be-database basebenzisa ngokunenzuzo lobu buhlobo ngokudala amathebula ane-subset yedatha evela kwelinye ithebula.
• Ubuhlobo obuningi kuya kokubili yihlobo oluvame kakhulu lobudlelwano be-database. Zenzeka uma irekhodi ngalinye kuThebula A lihambisana nerekhodi elilodwa noma ngaphezulu kuThebula B, kodwa irekhodi ngalinye kuThebula B lihambisana nerekhodi elilodwa kuThebula A. Isibonelo, ubuhlobo phakathi kwetafula labafundisi kanye netafula labafundi esikoleni esiphansi i-database ingaba ubuhlobo obuningi kuya phezulu, ngoba umfundi ngamunye unomfundisi oyedwa kuphela, kodwa uthisha ngamunye unabafundi abaningi. Lo mklamo ngamunye kuya kusiza ukuqeda idatha ephindaphindiwe.

• Ubuhlobo obuningi kuya kokuningi buba khona uma irekhodi ngalinye kuThebula A lihambisana nerekhodi elilodwa noma ngaphezulu kuThebula B, futhi irekhodi ngalinye kuThebula B lihambisana nelinye elilodwa noma ngaphezulu amarekhodi kuThebula A. Isibonelo, ubuhlobo phakathi koThisha kanye nezifundo Itafula lingase libe yiningi kakhulu ngoba uthisha ngamunye angafundisa izifundo ezingaphezu kweyodwa, futhi inkambo ngayinye ingaba nomfundisi ongaphezu kweyodwa.

Ukuzihlanganisa Ngokuzimela: Icala elikhethekile

Ukuzihlanganisa ngokuziqhenya kwenzeka uma kunetafula elilodwa elihilelekile. Isibonelo esisodwa esivamile ngetafula labasebenzi eliqukethe ulwazi mayelana nomphathi wesisebenzi ngasinye. Umphathi ngamunye uyisisebenzi futhi unomphathi wakhe. Kulesi simo, kukhona ubuhlobo obuningi bokubheka, njengoba isisebenzi ngasinye sinomqondisi oyedwa, kodwa umphathi ngamunye angaba nesisebenzi esingaphezu kwesisodwa.

Ukudala Ubudlelwano Namakhasimende Asemzini

Udala ubudlelwane phakathi kwamatafula ngokucacisa ukhiye wangaphandle .Lesi sitshalo sitshela i-database yokuxhumana ukuthi amatafula ahlobene kanjani. Ezimweni eziningi, ikholomu kuThebula A linezihluthulelo eziyisisekelo ezibhekiswe kuThebula B.

Cabangela futhi isibonelo samatafula abafundisi nabafundi. Itafula Labafundisi liqukethe i-ID kuphela, igama, nekholomu yokufunda:

Itafula labafundi liqukethe i-ID, igama, kanye nekholomu yangaphandle yesihluthulelo:

Ikholomu Teacher_FK etafuleni labaFundi libhekisela inani eliyinhloko lomfundisi wetafula labafundisi.

Ngokuvamile, abadwebi be-database bazosebenzisa i- "PK" noma "FK" egameni lekholomu ukuze babone kalula ukhiye oyinhloko noma ikholomu yangaphandle yekhiye.

Qaphela ukuthi lezi zibhebhe ezimbili zibonisa ubuhlobo obuningi kuya kokubili phakathi koothisha nabafundi.

Ubudlelwane nobuqotho bokuBheka

Uma usufake ukhiye wangaphandle etafuleni, ungabe usungula imithwalo yemininingwane eqinisekisa ukuthi ubuqotho bukhona phakathi kwamatafula amabili. Lokhu kuqinisekisa ukuthi ubudlelwane obuphakathi kwamatafula buhlala buvumelana. Lapho ithebula elilodwa linesihluthulelo sangaphandle kwelinye itafula, umqondo wokuthembeka okukhulunywa ngawo uthi noma yiliphi inani elingokhiye wangaphandle kuThebula B kufanele libheke kumarekhodi akhona kuThebula A.

Ukusebenzisa Ubudlelwano

Kuye ku-database yakho, usebenzise ubuhlobo phakathi kwamatafula ngezindlela ezahlukene. I-Microsoft Access inikeza idijithali evumela kalula ukuthi uxhumanise amatafula futhi futhi uqinisekise ukuthembeka okubalulekayo.

Uma ubhala ngokuqondile i-SQL, uzoqala ukudala ithebula labafundisi, ukumemezela ikholomu ye-ID ukuba kube ukhiye oyinhloko:

DALA ITHEBU Othisha (

I-InstructorID INT AUTO_INCREMENT I-PRIMARY KEY,
Teacher_Name VARCHAR (100),
I-Course VARCHAR (100)
);

Uma udala itafula labafundi, usho ikholomu ye-Teacher_FK ukuthi uyisihluthulelo sangaphandle esichaza ikholomu ye-InstructorID etafuleni labafundisi:

DALA TABLE Abafundi (
I-StudentID INT AUTO_INCREMENT I-PRIMARY KEY,
I-Student_Name VARCHAR (100), Teacher_FK INT,
ISIQEPHU ESIKHULU (Teacher_FK) REFERENCES Othisha (InstructorID))
);

Ukusebenzisa ubudlelwane ukujoyina amathebula

Uma usungule ubuhlobo obulodwa noma ngaphezulu ku-database yakho, ungasebenzisa amandla awo ngokusebenzisa imibuzo ye-SQL JOIN ukuhlanganisa ulwazi kusuka kumatafula amaningi. Uhlobo oluvame kakhulu lokujoyina yi-SQL INNER JOIN, noma ukujoyina okulula. Lolu hlobo lokujoyina lubuyisela wonke amarekhodi ahlangabezana nesimo sokujoyina kusuka kumatafula amaningi. Isibonelo, lokhu ku-JOIN isimo kuzobuyisela i-Student_Name, Teacher_Name, ne-Course lapho ukhiye wangaphandle etafuleni labaFundi kufana nesikhiye esiyinhloko etafuleni labafundisi:

HLOLA Abafundi.Student_Name, Teachers.Thisha_Name, Teachers.Course
FROM FROM Students
INNER JOIN Othisha
KWABAFUNDI.Teacher_FK = Teachers.InstructorID;

Lesi sitatimende sakha itafula into enjengale:

Ithebula elibuyiselwe kusuka ku-SQL Joyina Isitatimende

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