Define UNIQUE and NON-UNIQUE indexes for relations

5.1.3 Relational Model Notation We will use the following notation in our presentation: A relation schema R of degree n is denoted by R(A1, A2, ..., An). The uppercase letters Q, R, S denote relation names. The lowercase letters q, r, s denote relation states. The letters t, u, v denote tuples. . In general, the name of a relation schema such as STUDENT also indicates the current set of tuples in that relation-the current relation state-whereas STUDENT(Name, Son,...) refers only to the relation schema. An attribute A can be qualified with the relation name R to which it belongs by using the dot notation R.A-for example, STUDENT.Name or STUDENT.Age. This is because the same name may be used for two attri- butes in different relations. However, all attribute names in a particular relation must be distinct. An n-tuple t in a relation (R) is denoted by t = from corresponding to the attributes specified in the list. As an example, consider the tuple t = from the STUDENT relation in Fig. ure 5.1; we have tName} = , and t[Ssn, Gpa, Age] =