MySQL: Can not add foreign key into create table statement
I am not sure about word press, but if you are using MySQL then you need to change your foreign key structure
Original:

foreign key (fk_coupons_targets) references wp_frequentVisitorCoupons_coupons(couponId)


After adjust:

foreign key fk_coupons_targets (col_name) references wp_frequentVisitorCoupons_coupons(couponId)


example:

ALTER table_name
ADD CONSTRAINT constraint_name
FOREIGN KEY foreign_key_name(columns)
REFERENCES parent_table(columns)


Note: if you want to add them foreign key to create table then you need to add only the last two lines