> >> >>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.
In my book, referential constraints and foreign key constraints (the full name) are the same. > 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. I'm not going to do a serious answer on this one if this is really what you're doing. With regards, Martijn Tonies Database Workbench - tool for InterBase, Firebird, MySQL, Oracle & MS SQL Server Upscene Productions http://www.upscene.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
