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62 votes

An ER model of a database consists of entity types $A$ and $B$. These are connected by a relationship $R$ which does not have its own attribute. Under which one of the following conditions, can the relational table for R be merged with that of A?

  1. Relationship $R$ is one-to-many and the participation of $A$ in $R$ is total
  2. Relationship $R$ is one-to-many and the participation of $A$ in $R$ is partial
  3. Relationship $R$ is many-to-one and the participation of $A$ in $R$ is total
  4. Relationship $R$ is many-to-one and the participation of $A$ in $R$ is partial
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3 Answers

Best answer
42 votes
42 votes

The relation table for R should always be merged with the entity that has total participation and relationship should be many to one.

Answer is C.

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17 votes

(C) 

We need following two conditions:

  • A:B = Many to one
  • A has total participation

If A to B is many to one, then for each row in table A, the relationhip can be added as an extra column. Total participation ensures that there is no null values.

9 votes
9 votes
|A|===== <R> ---------|B|

here relation R between A and B represent many to one with total participation at A entity,

this representation is same as definition of week entity, ans is C
Answer:

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