There is no difference. The One & only Difference is a UNIQUE would

What is the difference between UNIQUE CONSTRAINT and
PRIMARY KEY?

1. There is no difference.
2. A PRIMARY KEY cannot be declared on multiple columns.
3. A UNIQUE CONSTRAINT cannot be declared on multiple
columns.
4. A table can have multiple PRIMARY KEYS but only one
UNIQUE CONSTRAINT.
5. A table can have multiple UNIQUE CONSTRAINTs but only
one PRIMARY KEY.

Question Posted / rajesh.m

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Answer Posted / rajesh.m

There is no difference.
The One & only Difference is a UNIQUE would allow Null
Values where as The Primary Key Not.

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