Both of these indexes uses "B-tree" structure but in Cluster index the "Leaf Node" actually points the physical data, but in Non-Cluster index it point’s to the "Row ID" and then the "Row ID" points to the "Leaf Node" of Cluster Index.
Below is the diagram of Cluster and Non-Clustered index.
|A table can have only one Cluster Index as it point to the physical data.
||A table can have more than one Non-Cluster Index as it only points to the pointer of Cluster Index.|
|Physical data is stored as per Cluster Index.
||There is no relation of physical data.|
|The leaf node of Cluster Index consist of data pages.
||The leaf node of Non-Clusted Index contain Index row.|
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