Foreign key across multiple databases

[Alan Hooker]

I have two tables on two databases

--
-- Database: `db2980298_agrimapper`
--

-- --------------------------------------------------------

--
-- Table structure for table `areaLevelZero`
--

CREATE TABLE `areaLevelZero` (
`id` int(2) NOT NULL auto_increment,
`areaLevelZeroID` varchar(36) collate utf8_unicode_ci NOT NULL,
`areaLevelCount` tinyint(1) NOT NULL,
`areaLevelZeroName` varchar(30) collate utf8_unicode_ci NOT NULL,
`active` enum('T','F') collate utf8_unicode_ci NOT NULL default 'F',
`isDeleted` tinyint(1) NOT NULL default '0',
`lastModified` timestamp NOT NULL default CURRENT_TIMESTAMP,
PRIMARY KEY (`areaLevelZeroID`),
KEY `id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci PACK_KEYS=0 AUTO_INCREMENT=251 ;

--
-- Triggers `areaLevelZero`
--
DROP TRIGGER IF EXISTS `db2980298_agrimapper`.`areaLevelZeroUUID`;
DELIMITER //
CREATE TRIGGER `db2980298_agrimapper`.`areaLevelZeroUUID` BEFORE INSERT ON `db2980298_agrimapper`.`areaLevelZero`
FOR EACH ROW BEGIN
IF NEW.areaLevelZeroID = '' THEN
SET NEW.areaLevelZeroID = UUID();
END IF;
END
//
DELIMITER ;
DROP TRIGGER IF EXISTS `db2980298_agrimapper`.`areaLevelZeroTimestampable`;
DELIMITER //
CREATE TRIGGER `db2980298_agrimapper`.`areaLevelZeroTimestampable` BEFORE UPDATE ON `db2980298_agrimapper`.`areaLevelZero`
FOR EACH ROW SET NEW.lastModified = NOW()
//
DELIMITER ;

and on db6901371_clients

--
-- Database: `db6901371_clients`
--

-- --------------------------------------------------------

--
-- Table structure for table `clients`
--

CREATE TABLE `clients` (
`clientID` tinyint(3) NOT NULL auto_increment,
`areaLevelZeroID` varchar(36) NOT NULL,
`areaLevelFourID` int(6) NOT NULL,
`clientName` varchar(30) NOT NULL,
PRIMARY KEY (`clientID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

when I try and create a FOREIGN KEY on db6901371_clients.clients FROM db2980298_agrimapper with root privalages

ALTER TABLE `db6901371_clients`.`clients` ADD FOREIGN KEY ( `areaLevelZeroID` ) REFERENCES `areaLevelZero`' ( `areaLevelZeroID` )

I get the error

Can't create table './db6901371_clients/#sql-e5_720.frm' (errno: 150)