What's the difference between a primary key and a unique key?

What's the difference between a primary key and a unique
key?

Question Posted / swapna

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What's the difference between a primary key and a unique key?..

Answer / swapna

Both primary key and unique enforce uniqueness of the
column on which they are defined. But by default primary
key creates a clustered index on the column, where are
unique creates a nonclustered index by default. Another
major difference is that, primary key doesn't allow NULLs,
but unique key allows one NULL only.

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16 Yes

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What's the difference between a primary key and a unique key?..

Answer / ramneet

There is one more diff b/w primary key and unique key that
there is only one primary key in a table but there are more
then one unique keys in a table.

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11 Yes

2 No

What's the difference between a primary key and a unique key?..

Answer / gowthami radhakrishnana

1)primary key uses clustered index
unique key uses non-clustered index

2)primary key doesn't allow null values
but unique allows one null value

3)there is only one primary key but more than one unique
keys

Is This Answer Correct ?

5 Yes

1 No

What's the difference between a primary key and a unique key?..

Answer / ramneet

Primary can be used in foregin key but unique key does not
used.

Is This Answer Correct ?

4 Yes

2 No

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