INFS 247 Lecture Notes - Lecture 8: Database, Foreign Key, Tuple
Document Summary
Most contemporary commercial dbms software packages are relational dbms (rdbms) In order for a table to be a relation the following conditions must hold . Within one table each each row must be unique. Within each row each value in each column must be single valued. All values in each column must be from the same domain (predefined) Collection of related relations within each relation has a unique name. Primary key: column(or a set of columns) whose value is unique for each row. Foreign keys: column in a relation that refers to a primary key column in another referred relation. A mechanism that is used to depict relationships in relational database model. For every occurrence of a foreign key to the corresponding primary key. The relation mapped from the entity on the m side of the 1:m relationship has a forein key that corresponds to the primary key of the relation mapped from the 1 side of the 1:m relationship.
