CS 3430 Lecture Notes - Lecture 15: Foreign Key, Data Domain, Unique Key

• School: App State
• Department: Computer Science
• Course: CS 3430
• Professor: Mohammad Mohebbi

Document Summary

Semantic integrity constraints: based on application semantics and cannot be expressed by the model. E(cid:454)a(cid:373)ple: (cid:862)the (cid:373)a(cid:454). (cid:374)o. of hours per e(cid:373)plo(cid:455)ee for all projects he or she (cid:449)orks o(cid:374) is (cid:1009)(cid:1010) hrs per (cid:449)eek(cid:863). A set s of relation schemas that belong to the same database. S is the name of the whole database schema. S = {r1, r2, , rn} and a set ic of integrity constraints. (cid:1005), (cid:1006), , (cid:374) are the (cid:374)a(cid:373)es of the i(cid:374)di(cid:448)idual relation schemas within the database s. Db is a relational database state of relational database schema s; S = {r1, r2, , rn} and ic. Db is a set of relation states. Db = {r1, r2, , rn} each ri is a state of ri. Each ri relation state satisfies the integrity constraints specified in ic. A relational database state is sometimes called a relational database snapshot. A database state that does not meet the constraints is an invalid state.