What distinguishes a clustered index from a regular index?

A clustered index is distinct from a regular index primarily because it dictates the physical order of the data within the table itself. When a clustered index is created on a table, the rows of the table are sorted and stored on disk according to the indexed columns. This means that the data is organized in the same order as defined by the clustered index, which allows for efficient retrieval of data, especially in queries that sort or filter by the indexed columns.

Because the clustered index determines how the data is stored, there can only be one clustered index per table, as the data can only be physically arranged in one order at a time. This feature of a clustered index contrasts with a non-clustered index, which maintains a separate structure that references the actual table rows and does not affect their physical order.

The other options address characteristics that aren’t core distinctions of clustered versus regular indexes. For instance, a copy of the indexed data might be relevant in specific contexts, but it does not define the fundamental difference. Data security and encryption relate to database protection measures, while unlimited data storage capacity is not a feature of either index type. Thus, the correct understanding of a clustered index is focused on its role in sorting and storing the actual data in the table in a