Multiple choices questions in DBMS, Interview questions in RDBMS, How referential integrity and cardinality ratio are related? How do we represent referential integrity in ER diagram? How to model referential integrity using cardinality ratios in entity relationship diagram?
RDBMS solved MCQ - Referential integrity and cardinality ratio in entity relationship model
1. A relationship R connecting entity sets E and F has referential integrity from E to F, i.e., the edge connecting R and F has an arrow directed towards F. Which among the following statements may be true?
a) R is many-to-many from E to F
b) R is many-to-one from E to F
c) R is many-to-one from F to E
d) R is one-to-one from E to F
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Answer: (b) R is many-one from E to F and (d) R is one-one from E to F Referential integrity is a constraint added to a many-to-one relationship in the “one direction.” Since a one-to-one relationship is a special case of a many-to-one relationship, R may be one-one from E to F. While reducing ER diagram into conceptual schemas, the primary key of the ONE side entity set will be added as the foreign key in the MANY side (or ONE side in one-to-one relationship) entity set. Example:
 In the ERD given above, Teacher is on ONE side and Subject is MANY side. After converting the ERD, the conceptual schemas are as follows; Teacher (ERP, Name, Qualification, Address, Phone) Subject (Sub_ID, Sub_Name, Syllabus, Medium, ERP) ERP in Subject is the foreign key that refers ERP of Teacher. |
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