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Difference between primary key and unique key ?
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Answer Posted / pramod paunikar
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 non-clustered index by default. Another
major difference is that, primary key does not allow NULLs,
but unique key allows only one NULL only.
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