What is the difference between a clustered and a non-clustered index?

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Accepted Answer

Clustered index determines the physical order of data in a table while non-clustered index creates a separate structure.

Clustered index sorts and stores the data rows in the table based on their key values.
Non-clustered index creates a separate structure that contains the key values and a pointer to the data row.
A table can have only one clustered index while multiple non-clustered indexes can be created.
Clustered index is faster for retrieving large amounts of data while non-clustered index is faster for retrieving small amounts of data.
Clustered index is automatically created when a primary key is defined while non-clustered index needs to be created manually.