I’m developing a helpdesk-like system, and I want to employ foreign keys, to make sure the DB structure is decent, but I don’t know if I should use them at all, and how to employ them properly.
Are there any good tutorials on how (and when) to use Foreign keys ?
edit The part where I’m the most confused at is the ON DELETE .. ON UPDATE .. part, let’s say I have the following tables
table 'users'
id int PK auto_increment
department_id int FK (departments.department_id) NULL
name varchar
table 'departments'
id int PK auto_increment
name
users.department_id is a foreign key from departments.department_id, how does the ON UPDATE and ON DELETE functions work here when i want to delete the department or the user?
You will need foreign keys if you are splitting your database into tables and you are working with a DBMS (e.g. MySQL, Oracle and others). I assume from your tags you are using MySQL.
If you don’t use foreign keys your database will become hard to manage and maintain. The process of normalisation ensures data consistency, which uses foreign keys.
See here for foreign keys. See here for why foreign keys are important in a relational database here.
Although denormalization is often used when efficiency is the main factor in the design. If this is the case you may want to move away from what I have told you.
Hope this helps.