Question

I want to know is it possible to do if I have 4 number as below

1,2,3,4

In my data base have data exists as below

1,2,3,5,6,7

How can I query database and return 4 in 1 query

Please advise

Answer 1

CREATE TABLE `example` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;

INSERT INTO example VALUES (1),(2),(3),(5),(6),(7);

SELECT t2.id FROM example AS t1
RIGHT JOIN (
  SELECT 1 AS id UNION
  SELECT 2 AS id UNION
  SELECT 3 AS id UNION
  SELECT 4 AS id
) AS t2
ON t1.id = t2.id
WHERE t1.id IS NULL;

+----+
| id |
+----+
|  4 |
+----+

Or use a temporary table:

CREATE TEMPORARY TABLE `tmp` (
  `id` int(11) DEFAULT NULL
) ENGINE=InnoDB;

INSERT INTO tmp VALUES (4);

SELECT t2.id FROM example AS t1
RIGHT JOIN tmp AS t2
ON t1.id = t2.id
WHERE t1.id IS NULL;

To see what’s happening, switch things around a bit:

SELECT t1.id, t2.id FROM example AS t1
RIGHT JOIN (
  SELECT 1 AS id UNION
  SELECT 2 AS id UNION
  SELECT 3 AS id UNION
  SELECT 4 AS id
) AS t2
ON t1.id = t2.id;

+------+----+
| id   | id |
+------+----+
|    1 |  1 |
|    2 |  2 |
|    3 |  3 |
| NULL |  4 |
+------+----+