What is the difference between clustered and non-clustered index in SQL?

See Microsoft Learn: Clustered and Nonclustered Indexes Described

Hi Norbert-8918,

Clustered index

• There can be only one clustered index per table.
• Clustered indexes sort and store the data rows in the table or view based on their key values.
• Clustered indexes sort the records and store them physically according to the order.
• Data retrieval is faster than non-clustered indexes.
• Clustered indexes do not consume extra space.

Non-clustered index

• There can be multiple non-clustered indexes per table.
• Non-clustered indexes have a structure separate from the data rows. A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value.
• Non-Clustered Indexes create logical order, and do not match physical stored order of the rows on disk.
• Data insert and update operation is faster than clustered index.
• Non-clustered indexes are stored in a separate place from the actual table claiming more storage space.

In addition, please refer to What is the difference between Clustered and Non-Clustered Indexes in SQL Server and this similar thread which might be helpful.

Best Regards,
Amelia

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