Tricky SQL - Select non-adjacent numbers

Question

Given this data on SQL Server 2005:

SectionID Name  
1         Dan  
2         Dan  
4         Dan  
5         Dan  
2         Tom  
7         Tom  
9         Tom  
10        Tom  

How would I select records where the sectionID must be +-2 or more from another section for the same name.

The result would be:

1 Dan  
4 Dan  
2 Tom  
7 Tom  
9 Tom

Thanks for reading!

Answer 1

SELECT *
FROM mytable a
WHERE NOT EXISTS
  (SELECT *
  FROM mytable b
  WHERE a.Name = b.Name
  AND a.SectionID = b.SectionID + 1)

Answer 2

Here's LEFT JOIN variant of Anthony's answer (removes consecutive id's from the results)

SELECT a.*
FROM mytable a 
     LEFT JOIN mytable b ON a.Name = b.Name AND a.SectionID = b.SectionID + 1
WHERE b.SectionID IS NULL

EDIT: Since there is another interpretation of the question (simply getting results where id's are more than 1 number apart) here is another attempt at an answer:

WITH alternate AS (
SELECT sectionid,
       name,
       EXISTS(SELECT a.sectionid 
              FROM mytable b 
              WHERE a.name = b.name AND 
                    (a.sectionid = b.sectionid-1 or a.sectionid = b.sectionid+1)) as has_neighbour,
       row_number() OVER (PARTITION by a.name ORDER BY a.name, a.sectionid) as row_no
FROM mytable a
)
SELECT sectionid, name 
FROM alternate
WHERE row_no % 2 = 1 OR NOT(has_neighbour) 
ORDER BY name, sectionid;

gives:

 sectionid | name 
-----------+------
         1 | Dan
         4 | Dan
         2 | Tom
         7 | Tom
         9 | Tom

Logic: if a record has neighbors with same name and id+/-1 then every odd row is taken, if it has no such neighbors then it gets the row regardless if it is even or odd.

As stated in the comment the condition is ambiguous - on start of each new sequence you might start with odd or even rows and the criteria will still be satisfied with different results (even with different number of results).