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If we declare constraints Unique and Not null on a single
column then it will act as a Primary key, so what is the use
of primary key??

Question Posted / asharilyas

Answers were Sorted based on User's Feedback



If we declare constraints Unique and Not null on a single column then it will act as a Primary key..

Answer / neha sinha

1) Primary key creates clustered index and unique key
creates non-clustered index. Performance wise clustered
index is fast so we need Primary key.
2)if we need more then one primary key in table than we can
use unique key+NOT NULL becous it behave as Primary key but
we cant define more than one column as primary key. :)

Is This Answer Correct ?    23 Yes 1 No

If we declare constraints Unique and Not null on a single column then it will act as a Primary key..

Answer / neha sinha

1) Primary key creates clustered index and unique key
creates non-clustered index. Performance wise clustered
index is fast so we need Primary key.
2)if we need more then one primary key in table than we can
use unique key+NOT NULL becous it behave as Primary key but
we cant define more than one column as primary key. :)

Is This Answer Correct ?    2 Yes 1 No

If we declare constraints Unique and Not null on a single column then it will act as a Primary key..

Answer / ashok

Internally , There is same as primary key and unique not null.
You can say unique + not null is higher step of primary key .
So there is no basic difference between this two.

Is This Answer Correct ?    7 Yes 11 No

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