Here is what I've tried so far:
mysql> alter table wp_delayedCoupons_visits remove foreign key fk_targets_visits;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'foreign key fk_targets_visits' at line 1
mysql> alter table wp_delayedCoupons_visits drop foreign key fk_targets_visits;
ERROR 1091 (42000): Can't DROP 'fk_targets_visits'; check that column/key exists
And also with backticks
mysql> alter table `wp_delayedCoupons_visits` remove foreign key `fk_targets_visits`;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'foreign key `fk_targets_visits`' at line 1
mysql> alter table `wp_delayedCoupons_visits` drop foreign key `fk_targets_visits`;
ERROR 1091 (42000): Can't DROP 'fk_targets_visits'; check that column/key exists
mysql> show columns in wp_delayedCoupons_visits;
+-------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+--------------+------+-----+---------+----------------+
| visitId | mediumint(5) | NO | PRI | NULL | auto_increment |
| visitorId | mediumint(9) | NO | | NULL | |
| urlVisited | varchar(500) | NO | | NULL | |
| fk_targets_visits | mediumint(5) | NO | UNI | NULL | |
+-------------------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
Does anyone have an idea what may causing the constraint not to drop or be removed?
You obviously have a column called fk_targets_visits, but not a foreign key constraint even named with a fk_ prefix.
look up by using
show create table `wp_delayedCoupons_visits`
if a forign key exists in this table, and then reissue your command by
alter table `wp_delayedCoupons_visits` drop foreign key fk_coup_visits
assuming a foreign key name fk_coup_visits really exists.