                        课程
                    
                        /数据库
                        
                            /MySQL
                        
                        /与MySQL的零距离接触

有人帮忙解析一下这段代码吗

SELECT student.sno,sname FROM student
WHERE NOT EXISTS(SELECT * FROM course WHERE EXISTS(SELECT * FROM sc WHERE student.sno=sc.sno and sc.cno=course.cno and cname='软件工程'));