Question

Consider the relational database with the following four schemas and their respective instances: \[ \text{Student(sNo, sName, dNo)} \text{       }\text{Dept(dNo, dName)} \\ \text{Course(cNo, cName, dNo)} \text{         } \text{Register(sNo, cNo)} \] 

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___________.

Hint:

In SQL, using the EXCEPT clause allows you to exclude certain rows from the results. Here, the query excludes courses that are already registered by the students.

Answer 1

Correct Answer: 2

SQL Query: \[ \text{SELECT FROM Student AS S WHERE NOT EXIST} \] \[ \left( \text{SELECT cNo FROM Course WHERE dNo = "D01"} \right) \] \[ \text{EXCEPT SELECT cNo FROM Register WHERE sNo = S.sNo} \] The number of rows returned by the above SQL query is: \[ \boxed{2}. \]