SELECT that returns list of values not occurring in any row

Question

Query:

select id from users where id in (1,2,3,4,5)

If the users table contains ids 1, 2, 3, this would return 1, 2, and 3. I want a query

Answer 1

A different option is to use another table containing all possible ids and then do a select from there:

mysql> describe ids;
+-------+-----------------+------+-----+---------+-------+
| Field | Type            | Null | Key | Default | Extra |
+-------+-----------------+------+-----+---------+-------+
| id    | int(5) unsigned | NO   |     | 0       |       |
+-------+-----------------+------+-----+---------+-------+
1 row in set (0.05 sec)

mysql> select * from ids;
+----+
| id |
+----+
|  1 |
|  2 |
|  3 |
|  4 |
|  5 |
+----+
5 rows in set (0.00 sec)

mysql> select * from users;
+----+
| id |
+----+
|  1 |
|  2 |
|  3 |
+----+
3 rows in set (0.00 sec)


mysql> select id from ids where id not in (select id from users);
+----+
| id |
+----+
|  4 |
|  5 |
+----+
2 rows in set (0.04 sec)

Added side effect - allows you to expand the result list by inserting into the ids table