SQL & PL/SQL

create table test(
snum int not null auto_increment,
course_id varchar(15),
primary key(course_id, snum))

create table testt(

course_id varchar(15),
pre_id varchar(15),
foreign key (course_id) references test(course_id),
foreign key (pre_id) references test(course_id))


the above two table test has a primary key (snum, course_id) . course_id, which is being referenced in below table testt as a foreign key.

i have an issue when trying to create a table test wit primary key (course_id, snum) that Error code 1075, SQL state 42000: Incorrect table definition; there can be only one auto column and it must be defined as a key. but when place primary key(snum, course_id) it's working in this case i wasn't able to use course_id as foreign key for below table testt.
could you please suggest me how to resolve this issue.