Answer / amith

PRIMARY KEY cannot be null, so essentially PRIMARY KEY is
equivalent to UNIQUE NOT NULL

Answer / raj

primary key is something which uniquely identifies the table
row. the value in primary key declared field can't be null
On the other hand unique avoids the duplicacy of data.

Answer / niraj kumar

primary key is not accept the null value.primary key is
always autoincrement.unique key is accept the one null
value.it is not a autoincrement.

Answer / manish

Primary Keys are used in building relationships between
tables in a database. (an index is automatically created on
the primary key). The difference between primary and
ordinary keys is that there can be multiple keys, but only
one primary key.

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