Project ForgeDatabase Management Systems
Relational Model & ER Basics
GATE 2012
Medium
Given the basic ER and relational models, which of the following is INCORRECT?
- AAn attribute of an entity can have more than one value
- BAn attribute of an entity can be composite
- In a row of a relational table, an attribute can have more than one value
- DIn a row of a relational table, an attribute can have exactly one value or a NULL value
Explanation
ER-model entities CAN have multi-valued or composite attributes (both TRUE statements), but the relational model requires every attribute value in a row to be atomic (a single value or NULL) — first normal form. So 'an attribute can have more than one value' in a relational table is the INCORRECT statement.
Source: GATE CS 2012 (2012)
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