Getting a `duplicate key` exception while adding a FK to the child table

[Jasmine Chacko]

I have a parent table called 'member' and the PK is Unsigned, autogenerated number named as 'memberId'.
In my second table called 'fine', I need to add a field called 'memberId' which will be an FK to member table. (I kept 'memberId'in fine table as the same datatype and also unsigned.

But I get the following error when I try to add this FK in fine table.

Please see below:

ERROR 1022: Can't write; duplicate key in table '#sql-2260_12'

SQL Statement:

ALTER TABLE `library`.`fine`
ADD CONSTRAINT `memberId`
FOREIGN KEY (`memberId`)
REFERENCES `library`.`member` (`memberId`)
ON DELETE NO ACTION
ON UPDATE NO ACTION

ERROR: Error when running failback script. Details follow.

ERROR 1050: Table 'fine' already exists

SQL Statement:

CREATE TABLE `fine` (
`fineId` int(11) unsigned NOT NULL,
`description` varchar(45) DEFAULT NULL,
`fineAmount` decimal(10,0) DEFAULT NULL,
`fineCollectedDate` date DEFAULT NULL,
`memberId` int(11) unsigned NOT NULL,
PRIMARY KEY (`fineId`),
UNIQUE KEY `fineId_UNIQUE` (`fineId`),
KEY `member_ID_idx` (`memberId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8