What is heap table?

Heap table:-

A table without cluster index is called Heap table. Now you are thinking why we are talking about this.

So as SQL developer we should aware and In next post I will explain which is related to maintenance how to Rebuild a heap table.

Now our next question is how to determine all the heap table from a database

so below is simplest query to determine all the heap tables from a  database

SELECT T.Name ‘Heaptable’
FROM sys.indexes I 
  INNER JOIN sys.tables T
  ON I.object_id = T.object_id
WHERE I.type = 0 AND T.type = ‘U’

I ran this query on Adventureworks database and 2 tables with heap as shown in below figure

What is extent?

Extents are  basic unit in which space is allocated to table or indexes.An extent is 8 contiguous pages .Each page is having size of 8k.