CSC 4710 Lecture Notes - Lecture 18: Relational Calculus, Query Language, Tuple

• School: Wayne State University
• Department: Computer Science
• Course: CSC 4710
• Professor: Dali Ismail

Document Summary

Csc 4710 lecture 18: chapter 13, relational calculus,visual query languages, and deductive databases. Sql and relational calculus: although relational algebra is useful in the analysis of query evaluation, sql is actually based on a different query language: relational calculus. T is the target a variable that ranges over tuples of values. Condition is the body of the query. Evaluates to true or false if a specific tuple is substituted for t. Tuple relational calculus: example: when a concrete tuple has been substituted for t: Teaching(t) is true if t is in the relational instance of teaching. T. semester = f2000" is true if the semester attribute of t has value f2000. Equivalent to: relation between sql and trc. Target t corresponds to select list: the query result contains the entire tuple: body split between two clauses: T. semester = f2000" corresponds to where clause: query result. P(t), where p is a relation name.