1．找出现管98所有学生的姓名、电话、地址： SELECT stu_name,phone,address
FROM student WHERE class_id IN (SELECT Class_id
FROM Class
WHERE Class_name='现管98')
当子查询返回一条记录时，“in”可以用“=”代替：
SELECT stu_name,phone,address FROM student WHERE class_id= (SELECT Class_id
FROM Class
WHERE Class_name='现管98')
或者：
SELECT stu_name,phone,address
FROM student WHERE EXISTS (SELECT *
FROM Class
WHERE Class_name='现管98' AND Class.Class_id=Student Class_id)
2、找出现管98所有任课老师的编号： SELECT Teac_id FROM CourseTeacher WHERE Class_id IN
(SELECT Class_id FROM Class
WHERE Class_name='现管98')
3、找出所有任教“c语言”老师的编号。 SELECT DISTINCT Teac_id FROM CoursgTeacher WHERE Course_id IN
(SELECT Course_id