数据库第三次作业

第三次作业

1. SQL命令查询李勇选修的课程号，成绩；（嵌套查询实现）

SELECT cno,grade                
 FROM   SC                       
 WHERE  sno IN
       (SELECT sno
        from Student      
        WHERE sname ='李勇');

2. SQL命令查询选修“数据库”的学生学号、姓名；（嵌套查询实现）

SELECT Sno,Sname            
 FROM    Student                             
 WHERE Sno  IN
          (SELECT Sno                 
           FROM    SC                       
           WHERE  Cno IN
               (SELECT Cno
                from course      
               WHERE cname ='数据库'));

3. SQL命令查询有不及格课程的学生学号、姓名；（嵌套查询实现）

SELECT Sno,Sname            
FROM  Student                             
WHERE Sno  IN
    (SELECT distinct Sno                 
      FROM  SC                       
      WHERE  grade<60) 

4. SQL命令查询没有不及格课程的学生学号；（嵌套查询、集合查询实现，）

第一种方法：
SELECT distinct Sno           
FROM  SC                              
WHERE Sno not IN
    (SELECT distinct Sno                 
      FROM  SC                       
      WHERE  grade<60)
第二种方法：    
SELECT distinct Sno           
FROM  SC                              
except
SELECT distinct Sno                 
FROM  SC                       
WHERE  grade<60

5. SQL命令查询选修学生“1001”修过的全部课程的学生姓名。

SELECT Sno,sname
FROM Student
WHERE NOT EXISTS
    (SELECT *
     FROM SC SCY
     WHERE SCY.Sno = ' 1001'  AND NOT EXISTS
            (SELECT *
             FROM SC SCZ
             WHERE SCZ.Sno=Student.Sno AND SCZ.Cno=SCY.Cno))