Relational Database Management Systems (RDBMS)

 Data is organized in tables defined by the relations of the data into organized tables.

Tables can have Primary AND/OR Unique keys.

They can also have Foreign Keys (FK)

Generally, each table/relation represents one "entity type" (such as customer or product - names of the tables).

Tables have columns and rows.

Every row represents an instance of related column values.

Primary Key represents NOT nullable values of a table and remain unique.

Unique Key also represents in a database relational modeling and implementation, a unique key (also known as a candidate key or just a key) is a set of attributes (columns) within a relational database table (also called a relation)

Foreign Key (FK) is a key to link 2 or more tables. FK is column/s in a table that refers to a PK in another table.