Mysql find id gaps in temporary table - mysql

Question

I need to find id gaps in a integer field of a temporary table.
Due to a temporary table limitation I cannot open the table twice and join it with itself.
This is the example:
CREATE TEMPORARY TABLE tmp_table (
id int(8) unsigned,
PRIMARY KEY (id)
);
INSERT INTO tmp_table VALUES (1),(2),(4),(7),(10),(11),(13);
and here I want to find this resultset:
3, 5, [6], 8, [9], 12
[#]=optional

Answer 1

A solution that works, but might be a better one.
This generates a range of numbers (so you will need to modify it for larger ranges - this copes up to 1000), and cross joins that range against the temp table. It finds the max and min ids from the temp table that are greater than or equal to or less or equal to (respectively) than generated value. Then in the HAVING clause check that the greater / less vales are not equal and also not null
SELECT 1 + units.i + tens.i * 10 + hundreds.i * 100 AS poss_num,
MAX(IF(tmp_table.id <= 1 + units.i + tens.i * 10 + hundreds.i * 100, tmp_table.id, NULL)) AS max_id,
MIN(IF(tmp_table.id >= 1 + units.i + tens.i * 10 + hundreds.i * 100, tmp_table.id, NULL)) AS min_id
FROM
(
SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
) units
CROSS JOIN
(
SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
) tens
CROSS JOIN
(
SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
) hundreds
CROSS JOIN tmp_table
GROUP BY poss_num
HAVING min_id != max_id
AND min_id IS NOT NULL
AND max_id IS NOT NULL