Returning Sequence of Numbers

For quite sometime, I use COLORDER column of syscolumns table to return a sequential number. I will usually pick a table with large number of columns enough to return my requirement. Until I come across Common Table Expression (CTE). One of the major difference between a CTE and a derived table or sub-query, is that a CTE can be self-referencing or recursive.

Consider returning a series of numbers 1-31.

Here's the code:

WITH Number_Sequence
AS
(
   SELECT 1 AS sequence
   UNION ALL
   SELECT sequence+1
   FROM Number_Sequence W
      WHERE sequence < 31
)
SELECT *
FROM Number_Sequence

Now that it's a result set, it may be used to join to another table. Since this is a CTE and not a physical table, it's not indexed and could degrade processing. Table size should always be considered before joining this CTE to another table.

Here's another sample code that simulate bit positions in a byte:

with GroupNumbers
as
(
   select 1 as byte, 1 as from_bit, 8 as to_bit
   union all
   select byte + 1, from_bit + 8, to_bit + 7
   from GroupNumbers
   where to_bit < 64
)  select * from GroupNumbers

As always, comments are welcome...


~~CK