Assertion. In terms of values allowed in a column, both UNIQUE and PRIMARY KEY constraints are not the same. Reason. UNIQUE allows NULL value once in the column, but PRIMARY KEY does not. 1. Both A and R are true and R is the correct explanation of A. 2. Both A and R are true but R is not the correct explanation of A. 3. A is true but R is false. 4. A is false but R is true.

Class - 12 CBSE Computer Science — Assertion Reason Type Questions

Assertion. In terms of values allowed in a column, both UNIQUE and PRIMARY KEY constraints are not the same.
Reason. UNIQUE allows NULL value once in the column, but PRIMARY KEY does not.
Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.

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Answer

Both A and R are true and R is the correct explanation of A.

Explanation
The UNIQUE and PRIMARY KEY constraints are similar in that they both ensure uniqueness of values in a column or set of columns. However, they differ in terms of the values they allow, particularly regarding NULL values. UNIQUE allows NULL values, whereas PRIMARY KEY does not.

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