Yes, you can create a clustered index on key columns that contain duplicate values. ... For example, you might decide to create a clustered index on the LastName column of a table that contains customer data.

Can non clustered index have duplicate values?

Unique Non Cluster Index only accepts unique values. It does not accept duplicate values. After creating a unique Non Cluster Index, we cannot insert duplicate values in the table.

Are clustered indexes unique?

Both clustered and nonclustered indexes can be unique. This means no two rows can have the same value for the index key. Otherwise, the index is not unique and multiple rows can share the same key value. For more information, see Create Unique Indexes.