ISYS114 Lecture 4: Isys114 Lecture 4

• School: Macquarie University
• Department: Information Systems
• Course: ISYS114
• Professor: Charanya

Document Summary

Exists independently of other types of entities. Dependent on a strong entity (identifying owner) (cid:272)a(cid:374)(cid:374)ot exist o(cid:374) its ow(cid:374) Does not have a unique identifier (only a partial identifier) Entity box and partial identifier have double lines. Each entity in the relationship will have exactly one related entity. An entity on one side of the relationship can have many related entities, but an entity on the other side will have a maximum of one related entity. Entities on both sides of the relationship can have many related entities on the other side. Cardinality constraints the number of instances of one entity that can or must be associated with each instance of another entity. People ofte(cid:374) (cid:272)o(cid:374)fuse the ter(cid:373) (cid:862)relatio(cid:374)(cid:863) with the ter(cid:373) (cid:862)relatio(cid:374)ship(cid:863). A relatio(cid:374) is a table that follows certain rules, and refers to actual relational database architecture. A relationship is a conceptual term that refers to how entities relate to each other.