mysql - unable to drop the foreign key

Question

I would like to drop the foreign key in my table but been into this error message

mysql> alter table customers drop foreign key customerid;
ERROR 1025 (HY000): Error on rename of '.productscustomers' to '.products#sql2-7ec-a3' (errno: 152)
mysql>

Answer 1

The solution described here by Chris White worked for me.

The root problem is that MySQL creates both an index and a foreign key. Both must be removed (the foreign key first contrary to what Chris said).

1. show create table table_name;

   SHOW CREATE TABLE `table_name`:
   
   | table_name | CREATE TABLE `table_name` (
     `id` int(20) unsigned NOT NULL auto_increment,
     `key_column` smallint(5) unsigned default '1',
     KEY `column_tablein_26440ee6` (`key_column`),  <--- shows key name
     CONSTRAINT `table_name_ibfk_1` FOREIGN KEY (`key_column`) REFERENCES <--- shows foreign key constraint name
   `second_table` (`id`) ON DELETE SET NULL
   ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
   

2. Delete the foreign key constraint:

   ALTER TABLE table_name DROP FOREIGN KEY `table_name_ibfk_1`;
   

3. Delete the key

   ALTER TABLE table_name DROP KEY `column_tablein_26440ee6`;
   

That did it for me.