Question

Basically I’m rather new to MySQL and in an example I see this foreign key being added:

ALTER TABLE Department ADD FOREIGN KEY managerIsInDepartment
(manager,id) REFERENCES Employee(id,worksAt);

I suppose one foreign key is being added (of the name managerIsInDepartment).

But I thought the attributes in the parentheses were the attributes to turn into foreign keys?

Why is managerIsInDepartment being displayed?

Answer 1

managerIsInDepartment is simply a name for the key to help identify it. You can omit it and one will be automatically generated.

ALTER TABLE Department <-- Table that will have the foreign key constraint
ADD <-- Option
FOREIGN KEY managerIsInDepartment  <-- Name of the key
(manager,id) <-- Columns included in the key
REFERENCES Employee <-- The table being referenced
(id,worksAt) <-- Columns being referenced in foreign table

Hope this helps.

A good reference.