getting values which dont exist in mysql table

Question

I have a set of values(keys), 1,2,3,4,5 and following table:

id key
------
1  2
2  8
3  4

If I need to check which of the given keys are in

Answer 1

While this is a very messy solution it does work:

select v.val from
(
  select 1 as val
  union
  select 2 as val
  union
  select 3 as val
  union
  select 4 as val
  union
  select 5 as val
) v
WHERE
v.val NOT IN(
  SELECT `key` 
  FROM mytable 
  WHERE key IN (1,2,3,4,5)
);