Consider the relational database with the following four schemas and their respective instances. $\text{Student}(\underline{\text{sNo}}, \text{sName}, \text{dNo})\quad \text{Dept}(\underline{\text{dNo}}, \text{dName})$ $\text{Course}(\underline{\text{cNo}}, \text{cName}, \text{dNo})\quad \text{Register}(\underline{\text{sNo}}, \underline{\text{cNo}})$ 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 ________.

The inner query computes the set difference:

1. Courses in Department D01: From the Course table, the courses with dNo = 'D01' are:

   $$\{\text{C11}, \text{C12}\}$$

2. Condition:WHERE NOT EXIST (...) is true if and only if the set difference is empty, meaning the student has registered for all courses offered by department D01 (i.e., both $\text{C11}$ and $\text{C12}$).

3. Evaluation for each student in Student:

   • S01 (James): Registered for $\{\text{C11}, \text{C12}\}$.

     $$\{\text{C11}, \text{C12}\} \setminus \{\text{C11}, \text{C12}\} = \emptyset \implies \text{TRUE}$$

   • S02 (Rocky): Registered for $\{\text{C11}\}$.

     $$\{\text{C11}, \text{C12}\} \setminus \{\text{C11}\} = \{\text{C12}\} \neq \emptyset \implies \text{FALSE}$$

   • S03 (Jackson): Registered for $\{\text{C21}, \text{C22}, \text{C23}\}$.

     $$\{\text{C11}, \text{C12}\} \setminus \{\text{C21}, \text{C22}, \text{C23}\} = \{\text{C11}, \text{C12}\} \neq \emptyset \implies \text{FALSE}$$

   • S04 (Jane): Registered for $\{\text{C11}, \text{C12}\}$.

     $$\{\text{C11}, \text{C12}\} \setminus \{\text{C11}, \text{C12}\} = \emptyset \implies \text{TRUE}$$

   • S05 (Milli): Registered for $\{\text{C11}, \text{C21}\}$.

     $$\{\text{C11}, \text{C12}\} \setminus \{\text{C11}, \text{C21}\} = \{\text{C12}\} \neq \emptyset \implies \text{FALSE}$$

Thus, exactly 2 rows (S01 and S04) are returned.