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CBSE Class 12 Computer Science Question 1 of 79

Table Creation and Data Manipulation Commands — Question 1

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Question

Question 1

Assertion. The PRIMARY KEY and UNIQUE constraints are the same.

Reason. The columns with PRIMARY KEY or UNIQUE constraints have unique values for each row.

Answer

(d)

Assertion is false but Reason is true.

Explanation
UNIQUE and PRIMARY KEY constraints are not the same and there are differences between them. Though both ensure unique values for each row in a column, but UNIQUE allows NULL values whereas PRIMARY KEY does not. Also, there can exist multiple columns with UNIQUE constraints in a table, but there can exist only one column or one combination with PRIMARY KEY constraint.