Sql statement: known student table student field student id student name class id course name exam results

Oracle Bone Inscriptions. (sql statements using sql server are mainly functional. I remember that sql server has nullif and no nvl).

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Select B. Class name, A. Course name, A. Average grade from (select class id, course name, avg(nvl (test score, 0)) Average grade from student group by class id, course name) A. Class B where A. Class id = B. Class ID.

(2)

Select * from student，(select student name，count(*)from student where exam results