Question

There is one table. Parent_id references same table id. How insert raw if parent_id = id? I don’t know id(before insert) and could’t insert if there is not parent_id.
What the optimal way without getting last INCREMENT id and creating temporary table?

CREATE TABLE `test` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `parent_id` int(11) unsigned NOT NULL,
  `someotherfield` varchar(45) NOT NULL,
  PRIMARY KEY (`id`),
  FOREIGN KEY `constr_catalog_guid_id` (`parent_id`) REFERENCES `test` (`id`)   
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

This is not work:

Insert into 'test' values (parent_id = test.id, "NOt matter");

Answer 1

CREATE TRIGGER trigger_increment_id_for_another_field BEFORE INSERT ON test FOR EACH ROW
BEGIN
   DECLARE next_id INT;
   SET next_id = (SELECT AUTO_INCREMENT FROM information_schema.TABLES WHERE TABLE_SCHEMA=DATABASE() AND TABLE_NAME='test');
   SET NEW.parent_id=next_id;
END

This trigger shall duplicate the parent_id value based on the auto_increment value for every insert of a row.