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1select de.sequence + 1 as sequence from dataentry as de 
2left outer join dataentry as de1 on de.sequence + 1 = de1.sequence
3where de1.sequence is null  order by sequence asc;
4	
5select (select isnull(max(val)+1,1) from mydata where val < md.val) as [from],
6     md.val - 1 as [to]
7  from mydata md
8  where md.val != 1 and not exists (
9        select 1 from mydata md2 where md2.val = md.val - 1)
10	
11from        to
12----------- -----------
136           6
148           8
1511          14
16	
17SELECT      #sequence.value
18FROM        #sequence
19LEFT JOIN   MyTable ON #sequence.value = MyTable.value
20WHERE       MyTable.value IS NULL
21	
22declare @min int
23declare @max int
24
25select @min = min(seq_field), @max = max(seq_field) from [Table]
26
27create table #tmp (Field_No int)
28while @min <= @max
29begin
30   if not exists (select * from [Table] where seq_field = @min)
31      insert into #tmp (seq_field) values (@min)
32   set @min = @min + 1
33end
34select * from #tmp
35drop table #tmp
36	
37SELECT  *
38FROM    (SELECT  row_number() over(order by number) as N from master..spt_values) t
39where   N not in (select 1 as sequence union  
40    	select 2 union 
41    	select 3 union 
42    	select 4 union 
43    	select 5 union 
44    	select 7 union 
45    	select 10 union 
46    	select 15
47    	)
48	
49SELECT  *
50FROM    (SELECT  row_number() over(order by number) as N from master..spt_values) t
51where   N not in (select 1 as sequence union  
52    	select 2 union 
53    	select 3 union 
54    	select 4 union 
55    	select 5 union 
56    	select 7 union 
57    	select 10 union 
58    	select 15
59    	)