What is a table called, if it has neither Cluster nor Non-cluster Index? What is it
Unindexed table or Heap. Microsoft Press Books and Book on Line (BOL) refers it as Heap.
A heap is a table that does not have a clustered index and, therefore, the pages are not
linked by pointers. The IAM pages are the only structures that link the pages in a table
together. Unindexed tables are good for fast storing of data. Many times it is better to drop
all indexes from table and then do bulk of inserts and to restore those indexes after that.