انواع التشاركيه بين الجداول (العلائقيه)
انواع المفاتيح للجداول (العلائقيه)

Pk - مفتاح رئيسي

Fk - مفتاح أجنبي - وهو مفتاح رئيسي فى جدوله

شكرا بس في مفتاح مرشح ومفتاح ثانوي كيف اميز بينهم

The difference between Primary Key and Secondary Key are stated below:-

Primary Key
1)	 Is used for Unique Identification of Rows
2)	We have only one Primary Key per table
3)	A Primary Key is one of the Candidate Keys or you can say one of the irreducible super key,
depends on database designer which one he needs.

Secondary Key
1)	Is used for Identification of Rows but not usually Unique
2)	We can have multiple Secondary Key per table
3)	Attribute used for Secondary key are not the ones used for Super Key
i.e. Secondary Key is not even be one of the Super Key.