create table firstk
(
id bigint unsigned not null auto_increment,
name char( 20 ),
primary key(id)
)type = InnoDB;

create table secondk
(
id bigint unsigned not null auto_increment,
fktest bigint unsigned,
name char( 20 ),
primary key(id),
foreign key(fktest) references firstk(id) on update cascade,
foreign key(fktest) references firstk(id) on delete set null
)type = InnoDB;

create table main_table
(
id bigint unsigned not null auto_increment,
fktest1 bigint unsigned, 
sktest1 bigint unsigned,
param_test double( 15 , 5 ) not null,
primary key(id),

foreign key(fktest1) references firstk(id) on update cascade,
foreign key(fktest1) references firstk(id) on delete set null,
foreign key(sktest1) references secondk(id) on update cascade,
foreign key(sktest1) references secondk(id) on delete set null
)type = InnoDB;

CREATE FUNCTION `test_key_secondk`(pk BIGINT)
    RETURNS BIGINT
    NOT DETERMINISTIC
    SQL SECURITY DEFINER
    COMMENT ''
BEGIN
DECLARE buf BIGINT UNSIGNED;
DECLARE CURMY CURSOR FOR SELECT 'secondk'.'fktest' FROM 'secondk' WHERE  'secondk'.'id'=pk;
OPEN CURMY;
FETCH CURNAME INTO buf;
RETURN buf;
END; 

CREATE FUNCTION `testkey_secondk`(fk BIGINT)
    RETURNS bigint( 20 )
    NOT DETERMINISTIC
    SQL SECURITY DEFINER
    COMMENT ''
BEGIN
DECLARE buf BIGINT UNSIGNED;
DECLARE cru CURSOR FOR SELECT secondk.fktest FROM secondk
WHERE  secondk.id=fk;
OPEN cru;
FETCH cru INTO buf;
CLOSE cru;
RETURN buf;
END;