Error 1215 Can't add foreign key constraint - mysql

Question

I've read several posts on this type of error (one of them was quite similar), but I haven't found one yet that resolves the error that I'm having with the foreign key. Since I can recreate the error, I think I have a pretty good idea of what it is. I am new to SQL, however, and I can't resolve the problem. Here's the code from the two affected tables:
create table artist (
artist_id int unsigned not null auto_increment,
first_name nvarchar(50) not null,
last_name nvarchar(50) not null,
about_artist nvarchar(550) not null,
start_of_event datetime,
end_of_event datetime,
item_id int unsigned not null,
user_id int unsigned not null,
last_modified timestamp,
primary key (artist_id),
foreign key (item_id) references
items (item_id),
foreign key (user_id) references
users (user_id)
);
create table items (
item_id int unsigned not null auto_increment,
artist_id int unsigned not null,
item_name nvarchar(50) not null,
item_description nvarchar(150) not null,
last_modified timestamp,
primary key (item_id),
foreign key (artist_id) references
artist(artist_id)
);
My item_id is item_id int unsigned not null, in the first table, but item_id int unsigned not null auto_increment, in the second table. The second table is the one where it is the primary key. I can't do two auto increments in one table, and if I reverse the order of the tables, the same thing happens with a different column. How can I resolve this? Thank you.

Answer 1

Thinking about my comment, I'm increasingly confident that the link table is the way you need to go.
create table artist (
artist_id int unsigned not null auto_increment,
first_name nvarchar(50) not null,
last_name nvarchar(50) not null,
about_artist nvarchar(550) not null,
start_of_event datetime,
end_of_event datetime,
user_id int unsigned not null,
last_modified timestamp,
primary key (artist_id),
foreign key (user_id) references
users (user_id)
);
create table items (
item_id int unsigned not null auto_increment,
artist_id int unsigned not null,
item_name nvarchar(50) not null,
item_description nvarchar(150) not null,
last_modified timestamp,
primary key (item_id)
);
create table artist_item (
artist_id int unsigned not null,
item_id int unsigned not null
foreign key (artist_id) references
artist(artist_id),
foreign key (item_id) references
items(item_id)
);
You could add an auto-increment field to artist_item, or have the two ID fields as a composite key.
With this, you can query for all items relating to an artist (e.g. one artist has several items):
select
*
from
artist_item join items on
artist_item.item_id = items.item_id
where
artist_item.artist_id = [ID]
or all artists related to an item (e.g. one item was worked on by several artists):
select
*
from
artist_item join artist on
artist_item.artist_id = artist.artist_id
where
artist_item.item_id = [ID]