SQL: Select Keys that doesn't exist in one table

Question

I got a table with a normal setup of auto inc. ids. Some of the rows have been deleted so the ID list could look something like this:

(1, 2, 3, 5, 8,

Answer 1

I have the same problem: I have a list of values from the user, and I want to find the subset that does not exist in anther table. I did it in oracle by building a pseudo-table in the select statement Here's a way to do it in Oracle. Try it in MySQL without the "from dual":

-- find ids from user (1,2,3) that *don't* exist in my person table
-- build a pseudo table and join it with my person table
select pseudo.id from (
  select '1' as id from dual
  union select '2' as id from dual
  union select '3' as id from dual
) pseudo
left join person
  on person.person_id = pseudo.id
where person.person_id is null