What are the different index configurations a table can have?

Question

My table is too big and now i realize that i need to add few columns in that, but when i tried to do this, my alter script took more then 4 hours and database performance also got degraded, so i canceled the query, can anyone suggest better way of doing that

Answer 1

A table can have one of the following index configurations:
No indexes
A clustered index
A clustered index and many nonclustered indexes
A nonclustered index
Many nonclustered indexes