Bulk insert into table with identity row

Question

hi,

 

I want to insert bulk data  into a new table with identity row like 

 

 1) 1 to 1,000 records under identity row A1

 2) 1,001 to 2,000 records under identity row A2

 3) 2,001 to 3,000 records under identity row A3

   :: 

   ::  

   ::

 10) 9,001 to 10,000 records under identity row A10

 from 10,001 to 11,000 records under B1

11,001 to 12,000 records under B2

12,001 to 13,000 records under B3

 ::

 :: 

 ::

19,001 to 20,000 records under B10

 

again new index 20,001 to 21,000 records under C1

 

 

Please share your ideas on the above