What is the referential integrety constant ?
Referential Integrity Constant :-
The referential integrity constant are specified between two relations and is used to maintain the consistency among tuples of the two relations.
The referential integrity constants states that a tuple in one relation that reefers to another relation must reefer to an existing tuple in that relation.
For exam, the attribute D.N.O of EMPLOYEE given the department number for which each employee works, hence its value in every ‘employee’ tuple must match the D NUMBER value of some tuple in the DEPARTMENT relation.
Tab-1
| EMPLOYEE | NAME | - | - | - | - | DNO |
| | Amal Bimal Kamal Shyamal | - - - - | - - - - | - - - - | - - - - | 5 5 4 1 |
Tab-2
| DEPARMENT | DNAME | DNUMBER | MGRSSN |
| | Research Administration Quarter | 5 4 1 | - - - |
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