Answer / pugal

Primary Key : The primary key of a relational table
uniquely identifies each record in the table

Foreign Key : These keys are used to create relationships
between tables.

Unique Key : In relational database design, a unique key is
a candidate key to uniquely identify each row in a table. A
unique key comprises a single column or set of columns

Difference between primary and unique key :

primary key not allows null values
unique key allows null values

Answer / nithya

one more difference is:

a table can have only one primary key but many unique keys.

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