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Difference between primary key and unique key ?
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Answer Posted / bhushan tatar
column having primary key constraint should not contain
null values.
column having unique key constraint can contain null values.
Unique as well as primary key constraint can be
defined/applyed on more than one column.
EX.
ADD constraint uc_person UNIQUE(P_Id,Lastname)
ADD constraint uc_person PRIMARY KEY(P_Id,Lastname)
But whle creating table we can write unique key word
multiple time and primary key wprd only once.Because table
can have only one primary key and can have miltiple unique
key.But both can apply on more than one column.
and
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