Programmatically display column names violating MySQL unique constraint with PHP - php

Question

When MySQL returns 23000 error code, it means that the update/insert query has triggered integrity constraint violation. However, the error, e.g.
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '22-offline-mpu-l' for key 'client_ad'
However, how to tell what are the columns that require unique combination?
The above table schema is:
CREATE TABLE `ad` (
`id` smallint(5) unsigned NOT NULL AUTO_INCREMENT,
`client_id` smallint(5) unsigned NOT NULL,
`slug` varchar(100) CHARACTER SET latin1 NOT NULL DEFAULT '',
`name` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
`status` tinyint(3) unsigned NOT NULL,
`width` smallint(5) unsigned NOT NULL,
`height` smallint(5) unsigned NOT NULL,
`code` varchar(2040) NOT NULL DEFAULT '',
PRIMARY KEY (`id`),
UNIQUE KEY `client_ad` (`client_id`,`slug`),
CONSTRAINT `ad_ibfk_1` FOREIGN KEY (`client_id`) REFERENCES `client` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=1746 DEFAULT CHARSET=utf8;

Answer 1

This is a proposal, rather than a definitive solution:
try {
// Query
} catch (\PDOException $e) {
if ($e->getCode() === '23000') {
// SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '22-offline-mpu-l' for key 'client_ad'
preg_match('/(?<=\')[^\']*(?=\'[^\']*$)/', $e->getMessage(), $match);
$columns = $this->db->prepare("
SELECT
`f1`.`name`
FROM
`information_schema`.`innodb_sys_tables` `t1`
INNER JOIN
`information_schema`.`innodb_sys_indexes` `i1` USING (`table_id`)
INNER JOIN
`information_schema`.`innodb_sys_fields` `f1` USING (`index_id`)
WHERE
`t1`.`schema` = DATABASE() AND
`t1`.`name` = :table_name AND
`i1`.`name` = :key_name AND
`i1`.`type` IN (2, 3)
ORDER BY
`f1`.`pos`;
")
->execute(['table_name' => static::$table_name, 'key_name' => $match[0]])
->fetchAll(\PDO::FETCH_COLUMN);
// $columns contains names of the columns that make up the index with the integrity constraint.
} else {
throw $e;
}
}
This uses regular expression to match the key name, then looks up the associated columns with the database, table and key name combination. innodb_sys_indexes.type 2 and 3 are the only (http://dev.mysql.com/doc/refman/5.6/en/innodb-sys-indexes-table.html) keys that (apply to tables) require unique values across the table.

Answer 2

It looks like the problem is with the foreign key referencing the client table, so I would do:
SHOW INDEXES FROM client WHERE Non_unique = 0;
and look at the columns you get back.
http://dev.mysql.com/doc/refman/5.0/en/show-index.html