Hi @rajesh yadav ,
Clustered index and unique non clustered index are ordered.
You can sort the records and store clustered index physically in memory as per the order. Allows you to stores data pages in the leaf nodes of the index.
A non clustered index contains the ordered data for the columns specified in that index, with pointers that tell us where to go to find the rest of the data from that row.
Suggest you read below blogs to get more information.
Clustered vs Non-clustered Index: Key Differences with Example
Clustered vs Nonclustered: What Index Is Right For My Data?
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