SQL，通过1条语句中的ALTER TABLE添加作为外键的列

Question

i want to extend a already created table by a column, but the column is a foreign key. This has to happen in 1 SQL statement. I know than i can use the ALTER TABLE operation to achieve it, but there is a small error message.

Existing Table:

//relation, because table already exists
Relation(A, B, C, D, E, F)

//creating a table F

CREATE TABLE `MyTable`(
`PK` INT(11) NOT NULL,
`H` VARCHAR(30) NOT NULL,
`I` INT NOT NULL,
PRIMARY KEY(`PK`),
FOREIGN KEY(`I`) REFERENCES `IT`(`I`)
);

Attempt to add the column I which is a foreign key(everything in one statement):

ALTER TABLE `R`
ADD COLUMN `PK` INT(11) NOT NULL,
ADD CONSTRAINT FOREIGN KEY (`PK`) REFERENCES `MyTable`(`PK`);

Error Message:

Cannot add or update a child row: a foreign key constraint fails.

Important: I know there could be a problem if the IT table has entries, but in our case, the table is empty.

Any suggestions?

EDIT: SOLUTION: Removed the constrain "NOT NULL". Thanks @Milan Švec

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

CREATE TABLE `MyTable`(
`PK` INT(11),
`H` VARCHAR(30) NOT NULL,
`I` INT NOT NULL,
PRIMARY KEY(`PK`),
FOREIGN KEY(`I`) REFERENCES `IT`(`I`)
);


ALTER TABLE `R`
ADD COLUMN `PK` INT(11),
ADD CONSTRAINT FOREIGN KEY (`PK`) REFERENCES `MyTable`(`PK`);

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

Answer 1

Not sure, but try to make the column nullable first. Change it to not nullable later, after filling by real values.