phpmyadmin

[witchy478]

Hi

 

I don't know if this is in the right place but I hope you can help.

 

I would like to know how to make foreign keys. I have looked on the internet but it's not making any sense to me. Some say that you can't make foreign keys and then others give you a way to make foreign keys but I don't understand them.

 

Can someone please tell me in a simple way how to do foreign keys.

 

I'm using phpmyadmin 3.4.10.1

 

Thank you

[The Little Guy]

Only the InnoDB supports "Real" Foreign Keys:

http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html

 

But you can have Foreign Keys in any other engine, but they won't be constant. With InnoDB, if you have a Primary Key and 10 tables that have a Foreign Key that points to the parent tables Primary Key, you can then update the primary key and all your foreign keys update along with it. In any other table you would have to update all the foreign keys manually.

 

That is as much as I have read/heard about Foreign Keys.

[scootstah]

Go to the "Structure" tab of a table and then click "Relation View" underneath the column definitions.

[witchy478]

Thanks for replying I tried to do the foreign keys and I get this error:

 

ERROR: Cannot add or update a child row: a foreign key constraint fails (`test`.`friend_emails`, CONSTRAINT `friend_emails_ibfk_3` FOREIGN KEY (`email_id`) REFERENCES `emails` (`id`) ON DELETE CASCADE ON UPDATE CASCADE)

[scootstah]

The parent row has to exist first.

[witchy478]

In my emails table i have id as the primary key and in my friend_emails I have email_id to use as my foreign key.

[scootstah]

A row has to exist in the emails table before you can create a row in the friend_emails table.

[sosdios]

If you want to read a simple explanation of foreign keys and how to use them appropriately, here's a pretty simple explanation: http://eliacom.com/wpForeignKeys.php. Once you've read through that, let me know if you're still have issues and we can work it out from there.

[witchy478]

I get an error saying: 

 

ERROR: Cannot add or update a child row: a foreign key constraint fails ('test"."friend_emails', CONSTRAINT 'friend_emails_ibfk_1' FOREIGN KEY('email_id') REFERENCES 'emails' ('email_id) ON UPDATE CASCADE)

 

In my emails table I have email_id, name, email, password.

My email_id is a primary key, it's type int(11), attributes unsigned.

 

In my friend_emails table I have id, email_id, friend1, friend2, friend3.

My id is the primary key, attributes unsigned.

My email_id is index, attributes unsigned.