What do "Internal Relations" do in phpMyAdmin for MyISAM tables?

Question

In phpMyAdmin v2.8.2.4 for MyISAM tables, the "Relation View" appears under the Structure tab. It shows a list of Internal Relations. But what do these do, given that MyISAM does not support foreign key constraints or relational integrity?

By phpMyAdmin version 3.2.0.1 this page ("Relation View") no longer appears for MyISAM tables. So does this mean that it wasn't doing anything in the first place?

Any explanations much appreciated. Justin

Tichon

Answer 1

Foreign keys in MyISAM are for advisory purposes only. You can look at them to see where the referential integrity would be, if there were any. It's easier to understand the schema that way than to guess relations by looking at the indexes created as a side-effect.

I don't know why it'd disappear in phpMyAdmin, unless it's a config issue (I believe the view can be disabled)?

Hadik

Thanks for your response - so there are no performance benefits from specifying the Internal Relation in MyISAM? (Yes, it may well be my config that is hiding the page for me in the latest version of phpMyAdmin, have not checked). – Tichon

No, the potential to affect performance comes from adding indexes, which is a side-effect of adding a foreign key (as well as something that can be done on its own of course). – Hadik