I am testing various scenarios of making SQL Select last 100 (top 100 order desc) records executing faster. The current PK constraint (on ORDER_NO) is non-clustered. I change it (in SSMS) from non-clustered to clustered. It took a little time (I understand that all non-clustered indexes have to be rebuilt). Now SQL Select works much faster and execution plan shows that the PK clustered index is used about 99%.
All seems to be good.
Two question:
1. Why by default when I was creating the PK (a while ago) SQL Server created non-clustered?
2. What are the downsides of making this PK clustered? It is an order number assigned and is never changed.
TIA
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