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)
);

Answer 2

This is a bit clunky, but it does work:

select sq.val
from   mytable t
       right join (select 1 as val
                   union 
                   select 2
                   union 
                   select 3
                   union 
                   select 4
                   union 
                   select 5 ) as sq
 on t.col = sq.val
 where t.id is null;

Obligatory SQL Fiddle.

Answer 3

Create temporary table with your keys:

CREATE TEMPORARY TABLE mykeys (`key` INT);
INSERT INTO mykeys VALUES (1),(2),(3),(4),(5);

Then use NOT IN:

SELECT `key`
FROM mykeys
WHERE `key` NOT IN (SELECT `key` FROM mytable)

Finally, drop your TEMP table if you must:

DROP TABLE mykeys

EDIT: Added SQLFiddle.

---

If you are using PostgreSQL which supports EXCEPT operator, and also VALUES statement can be used to create row set from list of values, there is another, easier way to do this without temporary tables (SQLFiddle):

VALUES (1),(2),(3),(4),(5)
EXCEPT
SELECT key FROM mytable