difference between primary key and foreign key
Primary Key :
It is unique column in every table in a database
It can ONLY accept;
- nonduplicate values
- cannot be NULL
Foreign Key:
It is a column that comes from a different table and
using Foreign key tables are related each other
It is the primary key of another table
It can be duplicate or null for another table
Unique Key:
Only unique value and also can contain NULL