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What's the difference between a primary key and a unique
key?
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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.
| Is This Answer Correct ? | 16 Yes | 0 No |
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.
| Is This Answer Correct ? | 11 Yes | 2 No |
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 |
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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