Database - Logical Database Design - Discussion

Discussion Forum : Logical Database Design - General Questions (Q.No. 1)
The entity integrity rule states that:
no primary key attribute may be null.
no primary key can be composite.
no primary key may be unique.
no primary key may be equal to a value in a foreign key.
Answer: Option
No answer description is available. Let's discuss.
3 comments Page 1 of 1.

Prashant said:   7 years ago
A table can have unique column value other than the primary key, and for that concept, option C may be correct.

Bhargav.k said:   9 years ago
Primary key is also satisfies the unique key. Unique key allows the null values but not the duplicate values.

Priyank said:   1 decade ago
In the relational data model, entity integrity is one of the three inherent integrity rules. Entity integrity is an integrity rule which states that every table must have a primary key and that the column or columns chosen to be the primary key should be unique and not null. A direct consequence of this integrity rule is that duplicate rows are forbidden in a table. If each value of a primary key must be unique no duplicate rows can logically appear in a table. The NOT NULL characteristic of a primary key ensures that its value can be used to identify all rows in a table.

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