Difference between primary key and unique key ?

Answer Posted / susil kumar rout

When we applied primary key constraint upon a column of a table internally oracle create a cluster index.In case of unique constraint,oracle create a non-cluster index.
In a table or entity one primary key and one or more than one
unique key can be applied.
We can't insert duplicate value or null value to primary key
column where as null value can insert into unique key column.

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