Queries for get unmatched passing values

Ok. Some confusion that I see here.

You list of (1,2,3,...,1000) does actually act as a table. If you have an actual list of numbers here (there are betters ways of generating a table like this) then use this as your select table. You will have to name the column if you wish to use it as the select

select ColA
from (
    select 1 as colA
    union select 2
    union select 3
    ...
    union select 1000)
where ColA not in(
   select t.ColA from table t)

I hope you see how awful this could be if you have to enter the sequence each time, and not in is not the most efficient method of discerning the missing values.

You can set up a tabular function that takes the list of numbers as, for example, a csv and returns a table, or you can use a Common Table Expression to set up the table on the fly. If you have a set 1 to n range then I would create this with a CTE.

The query below would be how I would do it:

DECLARE @UpperLimit int

set @UpperLimit = 1000

--CTE
    WITH mycte AS (
        SELECT 1 AS ColA
        UNION ALL SELECT ColA+ 1 FROM mycte
        WHERE ColA < @UpperLimit
    ) 
--mycte is now a table with ColA and 1-1000 as values
--CTE's are more efficient as they are evaluated in the select (below) so do not have to generate all values if there is a where clause

    SELECT m.ColA
    FROM mycte m
    WHERE NOT EXISTS (SELECT * FROM table1 t where m.ColA = t.ColA)
-- this is more efficient as the inner select does not have to perform the full query


--This might also be written with a tabular function:
   SELECT m.ColA
   FROM TableFromCSVFunction(@TheCsvNumbers) m
   WHERE NOT EXISTS (SELECT * FROM table1 t where m.ColA = t.ColA)
-- This is a lot less efficient as the whole function must complete before the select is performed

I hope that helps ^_^

Andy