Difference between primary key and unique key

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Accepted Answer

Primary key uniquely identifies a record in a table, while unique key ensures uniqueness of a column.

Primary key cannot have null values, while unique key can have one null value.
A table can have only one primary key, but multiple unique keys.
Primary key is automatically indexed, while unique key may or may not be indexed.
Example: Primary key - employee ID, Unique key - email address

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Accepted Answer

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Accepted Answer

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