Setting up foreign keys in phpMyAdmin?

Question

I'm setting up a database using phpMyAdmin. I have two tables (foo and bar), indexed on their primary keys. I am trying to create a relational table (foo_bar) between them, using their primary keys as foreign keys.

I created these tables as MyISAM, but have since changed all three to InnoDB, because I read that MyISAM doesn't support foreign keys. All id fields are INT(11).

When I choose the foo_bar table, click the "relation view" link, and try to set the FK columns to be database.foo.id and database.bar.id, it says "No index defined!" beside each column.

What am I missing?

Clarification/Update

For the sake of simplicity, I want to keep using phpMyAdmin. I am currently using XAMPP, which is easy enough to let me focus on the PHP/CSS/Javascript, and it comes with phpMyAdmin.

Also, although I haven't been able to set up explicit foreign keys yet, I do have a relational table and can perform joins like this:

SELECT *  FROM foo  INNER JOIN foo_bar  ON foo.id = foo_bar.foo_id  INNER JOIN bar ON foo_bar.bar_id = bar.id; 

It just makes me uncomfortable not to have the FKs explicitly defined in the database.

Answer 1

If you want to use phpMyAdmin to set up relations, you have to do 2 things. First of all, you have to define an index on the foreign key column in the referring table (so foo_bar.foo_id, in your case). Then, go to relation view (in the referring table) and select the referred column (so in your case foo.id) and the on update and on delete actions.

I think foreign keys are useful if you have multiple tables linked to one another, in particular, your delete scripts will become very short if you set the referencing options correctly.

EDIT: Make sure both of the tables have the InnoDB engine selected.

Answer 2

phpMyAdmin lets you define foreign keys using their "relations" view. But since, MySQL only supports foreign constraints on "INNO DB" tables, the first step is to make sure the tables you are using are of that type.

To setup a foreign key so that the PID column in a table named CHILD references the ID column in a table named PARENT, you can do the following:

1. For both tables, go to the operations tab and change their type to "INNO DB"
2. Make sure ID is the primary key (or at least an indexed column) of the PARENT table.
3. In the CHILD table, define an index for the PID column.
4. While viewing the structure tab of the CHILD table, click the "relation view" link just above the "add fields" section.
5. You will be given a table where each row corresponds to an indexed column in your CLIENT table. The first dropdown in each row lets you choose which TABLE->COLUMN the indexed column references. In the row for PID, choose PARENT->ID from the dropdown and click GO.

By doing an export on the CHILD table, you should see a foreign key constraint has been created for the PID column.