sql server - How to find the boundaries of groups of contiguous sequential numbers?

Question

I have a table with the following definition

CREATE TABLE mytable
  (
     id     INT IDENTITY(1, 1) PRIMARY KEY,
     number BIGINT,
     status INT
  )

and example data

INSERT INTO mytable
VALUES (100,0),
       (101,0),
       (102,0),
       (103,0),
       (104,1),
       (105,1),
       (106,0),
       (107,0),
       (1014,0),
       (1015,0),
       (1016,1),
       (1017,0)

Looking only at the rows where status = 0 how can I collapse the Number values into ranges of contiguous sequential numbers and find the start and end of each range?

i.e. For the example data the results would be

         FROM      to 
Number    100      103
Number    106      107
Number    1014     1015
Number    1017     1017

Answer 1

As mentioned in the comments this is a classic gaps and islands problem.

A solution popularized by Itzik Ben Gan is to use the fact that ROW_NUMBER() OVER (ORDER BY number) - number remains constant within an "island" and cannot appear in multiple islands.

WITH T
     AS (SELECT ROW_NUMBER() OVER (ORDER BY number) - number AS Grp,
                number
         FROM   mytable
         WHERE  status = 0)
SELECT MIN(number) AS [From],
       MAX(number) AS [To]
FROM   T
GROUP  BY Grp
ORDER  BY MIN(number) 

NB: If number is not guaranteed to be unique replace ROW_NUMBER with DENSE_RANK in the code above.