Why my table doesnt support FOREIGN KEYS?

Question

I have made a database and 10 tables in mysql(table type NONE) and i can\'t create foreign keys. An alert message says

SQLyog The selected table does not support for

Answer 1

Typically, InnoDB is used to support foreign keys, and transactions:

http://dev.mysql.com/doc/refman/5.1/en/innodb.html

You can change the table engine on the fly:

ALTER TABLE tableName ENGINE = InnoDB;

You can also change the default -- for newly created tables -- as shown here:

http://dev.mysql.com/doc/refman/5.1/en/storage-engine-setting.html

Answer 2

The engine you're using doesn't support foreign keys (as the error message tells you obviously). You can change the engine you're using with

ALTER TABLE `tableName` ENGINE = newEngine;

Answer 3

Yes. The default storage engine (MyISAM) does not support foreign key constraints.

Answer 4

I was having same problem until I found this post.

For addressing the limitation of MyISAM or NDB (Cluster), constraints can be enforced using triggers.

Answer 5

The MyISAM engine DOES support foreign keys. What it doesn't support is foreign key constraints.

You can go ahead and create as many foreign keys as you like - but don't expect the database to enforce integrity for you.

Don't change engines in your application without significant testing; changing engine will affect behaviour and is not recommended without great care and a lot of QA work. In particular, switching from MyISAM to InnoDB will break your application if:

• It doesn't handle deadlocks appropriately (Deadlocks do not happen on MyISAM)
• It expects table-level locking
• It relies on (mostly dubious) MyISAM features
• It is high performance and you have not understood how to tune InnoDB correctly, but did tune MyISAM well (or ok)
• You have not assessed the disc space impact of switching engines