Question

I have a self-referential MySQL table with a recursive parent_id:

CREATE TABLE `recursive` (   `id` int(11) NOT NULL auto_increment,   `parent_id` int(11) default NULL,   `name` varchar(100) NOT NULL,   PRIMARY KEY  (`id`),   KEY `data_categorysource_parent_id` (`parent_id`),   CONSTRAINT `parent_id_refs_id_627b4293`     FOREIGN KEY (`parent_id`) REFERENCES `data_categorysource` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 

During testing, I want to empty it but TRUNCATE fails:

TRUNCATE `recursive`  /* SQL Error: Cannot delete or update a parent row: a foreign key constraint fails... 

I currently have to manually delete all records, starting at the bottom of the tree working upwards. This gets onerous even with small trees.

Is there an easy way around this? I can’t DROP the table and re-create it easily as other tables reference it (I have already truncated those so there should be no data integrity issues there).

Answer 1

Why not:

UPDATE 'recursive' SET 'parent_id' = NULL WHERE 'parent_id' IS NOT NULL; DELETE FROM 'recursive'; 

?