>> >>key relationships?
>> > MyISAM can't FK's.
>> Yes it can, they're just not enforced.
> LOL - that's just like saying that MyISAM supports transactions
> if you only do transactions that are a single statement...
> In other words: useles.
Somehow I use these "useles" foreign keys to create relational databases.
A foreign key is merely a column which references a primary key or a unique
key in the same or another table.
I think you're confusing referential constraints with foreign keys. Even in
database systems that support referential constraints and cascade
dependencies, the usage of such constraints on foreign keys is optional and
dependant on your desire to trade-off referential integrity for performance.
In some systems, the performance penalty of enforcing referential
constraints and doing deletions in dependant tables simply cannot be
afforded during high usage hours for databases that serve real-time systems
(I work in telecom for example), and therefore one may choose to implement a
cleanup process during very low usage hours in the middle of the night to
find orphaned records, delete them, and then optimize the table. This
allows you to avoid deleting anything but the primary record while people
are waiting on the phone, which for MyISAM has the added benefit of allowing
concurrent insert/select to continue in the dependent tables.