SQL

Consider the relational database with the following four schemas and their respective instances (see figure). Student(sNo, sName, dNo) Dept(dNo, dName) Course(cNo, cName, dNo) Register(sNo, cNo) SQL Query:

SELECT * FROM Student AS S WHERE NOT EXIST
  (SELECT cNo FROM Course WHERE dNo = "D01"
     EXCEPT
   SELECT cNo FROM Register WHERE sNo = S.sNo)

The number of rows returned by the above SQL query is __________