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28 votes
28 votes

Given the basic ER and relational models, which of the following is INCORRECT?

  1. An attribute of an entity can have more than one value
  2. An attribute of an entity can be composite
  3. In a row of a relational table, an attribute can have more than one value
  4. In a row of a relational table, an attribute can have exactly one value or a NULL value
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5 Answers

Best answer
42 votes
42 votes

(C) is incorrect as a relational table requires that, in a row, an attribute can have exactly one value or NULL value.

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4 votes
4 votes
The term ‘entity’ belongs to ER model and the term ‘relational table’ belongs to relational model.

A and B both are true. ER model supports both multivalued and composite attributes See this for more details.

(C) is false and (D) is true. In Relation model, an entry in relational table can can have exactly one value or a NULL.
1 votes
1 votes
Option C is correct.
 
 First Two options are related to ER Model and In E-R diagram we can have multi valued and composite attributes so those two options are correct.
            Last Two options are related to Relational model 
According to Relational Model every relation should be in 1NF and according to 1 NF, there should not be a multi-valued attribute in a relation. That means an attribute can have only one value or NULL value in a row. So statement of option C is incorrect
0 votes
0 votes

Option C is correct.

According to Relational Model every relation should be in 1NF and according to 1 NF, there should not be a multivalued attribute in a relation. That means an attribute can have only one value or NULL value in a row. So statement of option C is incorrect

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