ER-Model
August 9, 2024Database-Management-System
August 9, 2024Database-Management-System
| Question 902 |
| An attribute of an entity can have more than one value
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| An attribute of an entity can be composite
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In a row of relational table, an attribute can have more than one value
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| In a row of relational table, an attribute can have exactly one value or a NULL value |
“In a row of a relational table, an attribute can have more than one value.”
In a relational database model, each attribute within a table should contain a single, atomic value for each row. The concept of atomicity is one of the fundamental principles of the relational model. Each cell in a relational table should contain a single, indivisible value, not multiple values.
The other statements are correct:
“An attribute of an entity can have more than one value” refers to a multi-valued attribute in the Entity-Relationship (ER) model, which is a valid concept in the ER model but is typically represented differently in a relational database.
“An attribute of an entity can be composite” is true. Composite attributes in the ER model can be broken down into multiple simple attributes in a relational table.
“In a row of a relational table, an attribute can have exactly one value or a NULL value” is also correct. In the relational model, attributes can have single values or be NULL to represent missing or unknown data.
“In a row of a relational table, an attribute can have more than one value.”
In a relational database model, each attribute within a table should contain a single, atomic value for each row. The concept of atomicity is one of the fundamental principles of the relational model. Each cell in a relational table should contain a single, indivisible value, not multiple values.
The other statements are correct:
“An attribute of an entity can have more than one value” refers to a multi-valued attribute in the Entity-Relationship (ER) model, which is a valid concept in the ER model but is typically represented differently in a relational database.
“An attribute of an entity can be composite” is true. Composite attributes in the ER model can be broken down into multiple simple attributes in a relational table.
“In a row of a relational table, an attribute can have exactly one value or a NULL value” is also correct. In the relational model, attributes can have single values or be NULL to represent missing or unknown data.