Key Terms

business rules: obtained from users when gathering requirements and are used to determine cardinality

cardinality: expresses the minimum and maximum number of entity occurrences associated with one occurrence of a related entity

connectivity: the relationship between two tables, e.g., one to one or one to many

constraints: the rules that force DBMSs to check that data satisfies the semantics

entity integrity: requires that every table have a primary key; neither the primary key, nor any part of it, can contain null values

identifying relationship: where the primary key contains the foreign key; indicated in an ERD by a solid line

integrity constraints: logical statements that state what data values are or are not allowed and which format is suitable for an attribute

mandatory relationship:one entity occurrence requires a corresponding entity occurrence.

non-identifying relationship: does not contain the foreign key in the primary key; indicated in an ERD by a dotted line

optional relationship: the FK can be null or the parent table does not need to have a corresponding child table occurrence

orphan record: a record whose foreign key value is not found in the corresponding entity – the entity where the primary key is located

referential integrity: requires that a foreign key must have a matching primary key or it must be null

relational database management system (RDBMS): a popular database system based on the relational model introduced by E. F. Codd of IBM's San Jose Research Laboratory

relationship type: the type of relationship between two tables in an ERD (either identifying or non-identifying); this relationship is indicated by a line drawn between the two tables.