MySQL - delete rows rejected on INNODB table - mysql

Question

I have two tables - a user table and a userlog table.
CREATE TABLE `client_user` (
`id_client_user` int(11) NOT NULL auto_increment,
`Nom` varchar(45) NOT NULL,
`Prenom` varchar(45) NOT NULL,
`email` varchar(255) NOT NULL,
`userid` varchar(45) NOT NULL,
`password` varchar(45) NOT NULL,
`active` tinyint(1) NOT NULL default '0',
`lastaccess` timestamp NULL default NULL,
`user_must_change_pwd` tinyint(1) NOT NULL default '0',
PRIMARY KEY (`id_client_user`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE `user_log` (
`id_user_log` int(11) NOT NULL auto_increment,
`access` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
`zone_updated` varchar(255) NOT NULL,
`id_client_user` int(11) NOT NULL,
PRIMARY KEY (`id_user_log`),
KEY `fk_user_log_client_user1` (`id_client_user`),
CONSTRAINT `fk_user_log_client_user1`
FOREIGN KEY (`id_client_user`)
REFERENCES `client_user` (`id_client_user`)
ON DELETE NO ACTION
ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
I create a user in the client_user table and then his activity is logged within the user_log table.
I now need to delete rows in the user_log table.
This is rejected because of the foreign key constraint - that much I have understood.
After having looked at the documentation, I have not seen how I can change the foreign key to allow me to delete the user_log records.
What I need is a foreign key (1:n), client_user (1) to user_log (n), where user_log records can be deleted without impacting the associated client_user record.
I am sure that this is possible with innodb, but I cannot see how.
Help ?

Answer 1

From the specification
InnoDB supports the use of ALTER TABLE to drop foreign keys:
ALTER TABLE tbl_name DROP FOREIGN KEY fk_symbol;