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It defines that the tuple in one relation that refers to another relation must refer to an existing tuple in that relation. This constraint is states on two relations (not essentially distinct). It uses a concept of foreign key and has been dealt with in more factors in the next unit.
Example
In the example given above, the value of C^ in every R tuple is matching with the value of C# in some S tuple. If a tuple has values (A6, B2, and C4) is added then it is invalid as referenced relation S doesn't contain C4. Therefore, it will be a violation of referential integrity constraint.
Explain Candidate key? Candidate Key - A candidate key is a minimal superkey, that can be used to uniquely identify a tuple in the relation.
Consider the subsequent relation Professor (Pfcode, dept, head, time) It is assumed that (i) A professor can work in much more than one
explaination
A database for the Service and Maintenance (SM) section of a Computer sales and service Company has to be developed. SM gives after sales service to customers. SM branch has a numb
Example - ALTER TABLE emp MODIFY (empno NUMBER (7));
Making Common Behaviour Abstract Let us define abstraction "Abstraction means to focus on the necessary, inherent aspects of an entity and ignoring its accidental features". O
Describe the host language? Host Language: You could write applications along with SQL statements embedded inside a host language. The SQL statements give the database inter
NEED FOR A DATABASE MANAGEMENT SYSTEM A Database is a structured, persistent collection of data of an organisation. The database management system (DBMS) manages the database o
Draw an ER diagram for company''s database schema
Explain CNT in the respects of QBE ? CNT: It is one of the aggregation commands given in QBE. It is used to identify number of tuples
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