Basic terminology:
- Key: One or more columns used to identify a row.
- Primary KEY (Primary key): A unique identifying keyword represented as a record (row), with only one primary key in a table. Also called the primary key.
- Hou keyword (candidate key): a property set that uniquely identifies a row in the table without the extra attributes.
- Common keyword (Common key): The relationship between relationships is represented by a compatible or identical attribute or attribute group. If two relationships have a compatible or identical attribute or attribute group, then this attribute or attribute group is called a common keyword for two relationships.
- Foreign keyword (Foreign key): If the public key is a primary key in a relationship, then this common keyword is called the foreign key of the other relationship. So, the connection between the two relationships, also known as the foreign key.
- ！ The name of the primary key and foreign key can be different, but the type must be the same!
3. Relational database Terminology
