[tomnipotent]

Any table in SQL Server without a clustered index will be stored as a heap.

https://docs.microsoft.com/en-us/sql/relational-databases/in...

[hans_castorp]

Yes, but the _default_ (and that's what I was referring to) is a clustered index.

[tomnipotent]

Then the definition depends on whether you consider adding a primary key as default or not. I would not consider it default, though it is customary.