Answer / ravi kanth

Primary key is the combination of unique and not null.But
unique key accepts null values also.

Answer / suresh kumar somayajula

Unique Key allows NULL value and a table can have more than
one UNIQUE KEY Constraint.

Primary Key is the combination of UNIQUE+NOT NULL,means it
won't allow NULL Values and a table can have only one
Primary Key.But a table can have Composite Primary Key.

Thank you,
Suresh

Answer / priyanka

Both are uniqe identification keys but Primary key should
not be null but uniqe key should.

Answer / divyarao

primary key accepts only values which has no duplication ,and does not accept null values . for a a table there should be only one primary key constraint.
whereas in unique key ,it accepts null values .here also there should not be any duplication ,a table may have more than one unique key constarint

Answer / vinod

uniqe key allow one null value only but primary key cannot
allow any null value

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