162 SQL — The Relational Language
(c) list the top three instructors in the order of the number of courses they taught. 45. Let GRAPH be the table introduced in Example 5.20.3. The degree of a vertex is the number of edges incident to that vertex. (a) write an SQL query that yields a list of vertices of a graph arranged in the decreasing order of their degrees; (b) list the top 5 vertices of a graph in increasing order of their degrees. 46. For each instructors list the sequence of the numbers of courses that the instructor taught during each of the semesters that he or she was active. 47. List the top three instructors in the order of the number of students that they advise.
5.26 Bibliographical Comments
The initial standard known as SQL1 is recorded in citeX3,ISO7. SQL2 was defined in [International Organization for Standardization, 1992]. Extensive presentations of SQL3 can be found in [Melton and Simon, 1993; Melton and Simon, 2002] and [Fortier, 1999]. Also, useful reference are [Line and Kline, 2000] and [J. Kauffman, 2001].