What are the differences between Primary Key & Foreign Key.

Difference between Primary Key & Foreign Key.

Primary Key

  • Primary key uniquely identify a record in the table.
  • Primary Key can’t accept null values.
  • By default, Primary key is clustered index and data in the database table is physically organized in the sequence of clustered index.
  • We can have only one Primary key in a table.

Foreign Key

  • Foreign key is a field in the table that is primary key in another table.
  • Foreign key can accept multiple null value.
  • Foreign key do not automatically create an index, clustered or non-clustered. You can manually create an index on foreign key.
  • We can have more than one foreign key in a table.
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