SQL Server 数据查询 --- 复杂查询

/********************************************

例1查询每个学生及其选修课程的情况

*********************************************/

SELECT STUDENT.*,SC.* FROM SC,STUDENT WHERE SC.SNO = STUDENT.SNO;

 

/********************************************

对例1用自然连接完成

*********************************************/

SELECT STUDENT.SNAME,STUDENT.SSEX,STUDENT.SAGE,STUDENT.SDEPT,SC.* 
FROM SC,STUDENT        
WHERE SC.SNO = STUDENT.SNO;

/*****************************************

查询每一门课程的间接先修课

*****************************************/

SELECT SY.CNO,SX.CPNO FROM COURSE SX,COURSE SY WHERE SX.CNO = SY.CPNO

 

/********************************************

对例1用左外连接连接完成

*********************************************/

SELECT STUDENT.SNAME,STUDENT.SSEX,STUDENT.SAGE,STUDENT.SDEPT,SC.* 
FROM   STUDENT LEFT JOIN SC ON(SC.SNO = STUDENT.SNO);

/********************************************

查询每个学生的学号、姓名、选修的课程名及成绩 *********************************************/

SELECT STUDENT.SNO,STUDENT.SNAME,COURSE.CNAME,COURSE.CCREDIT 
FROM SC,STUDENT,COURSE    
WHERE SC.CNO =COURSE.CNO AND SC.SNO = STUDENT.SNO;

 

/********************************************  

查询与刘晨在同一个系学习的学生

*********************************************/

SELECT SX.* 
FROM STUDENT SX    
WHERE SX.SDEPT IN  ( 
             SELECT SY.SDEPT FROM STUDENT SY WHERE SY.SNAME='刘晨' 
); 

/************   

或者如下:

SELECT SX.* 
FROM STUDENT SX, STUDENT SY       
WHERE SX.SDEPT = SY.SDEPT AND SY.SNAME = '刘晨';  

或者：

SELECT * 
FROM STUDENT SX 
WHERE EXISTS ( 
         SELECT * FROM STUDENT SY WHERE SY.SDEPT = SX.SDEPT AND SY.SNAME='刘晨'
);  

**************/

 

/********************************************  

查询选修了课程名为"信息系统"的学生学号和姓名 *********************************************/

SELECT SNO, SNAME 
FROM STUDENT        
WHERE SNO IN  ( 
        SELECT SNO FROM SC 
        WHERE  CNO IN  ( 
                    SELECT CNO FROM COURSE
                    WHERE CNAME = '信息系统'
                    ) 
);   

/********************************************  

找出每个学生超过他选修课程平均成绩的课程号

*********************************************/

SELECT SX.SNO,SX.CNO 
FROM SC SX 
WHERE SX.GRADE  >  (
                       SELECT AVG(GRADE) 
                       FROM SC SY               
                       WHERE SX.SNO = SY.SNO
);

 

/*****************************************************  

查询其他系中比计算机科学系某一学生年龄小的学生姓名和年龄

*******************************************************/

SELECT SNAME, SAGE 
FROM STUDENT    
WHERE SAGE < ANY  (
                      SELECT SAGE 
                      FROM STUDENT  
                      WHERE SDEPT='CS'
                   )
      AND SDEPT<>'CS';

 

/*****************************************************  

查询其他系中比计算机科学系所有学生年龄小的学生姓名和年龄

*******************************************************/

SELECT SNAME, SAGE 
FROM STUDENT    
WHERE SAGE < ALL  (
                      SELECT SAGE 
                      FROM STUDENT  
                      WHERE SDEPT='CS'  
                   )
      AND SDEPT<>'CS';

/*****************************************************  

查询所有选修了1号课程的学生姓名

*******************************************************/

SELECT SNAME 
FROM STUDENT    
WHERE EXISTS   ( 
                  SELECT * FROM SC            
                  WHERE SC.SNO = STUDENT.SNO AND SC.CNO='1'           
);

 

/******************************************

查询选修了全部课程的学生姓名

*******************************************/

SELECT SNAME 
FROM STUDENT 
WHERE NOT EXISTS ( 
                    SELECT * 
                    FROM COURSE 
                    WHERE NOT EXISTS   ( 
                                          SELECT * 
                                          FROM SC 
                                          WHERE STUDENT.SNO = SC.SNO AND COURSE.CNO = SC.CNO
                                        )
);

/*****************************************************

查询至少选修了学生200215122选修的全部课程的学生号码

*****************************************************/

SELECT DISTINCT SNO 
FROM SC X     
WHERE NOT EXISTS ( 
                    SELECT * 
                    FROM SC Y 
                    WHERE SNO='200215122' AND NOT EXISTS ( 
                                                            SELECT * 
                                                            FROM SC Z 
                                                            WHERE Z.SNO = X.SNO AND Y.CNO = Z.CNO              
                                                          )
); 

/**********************************************************

从自身表中选择一条记录，修改某个字段再回插到自身表中

这里的INSERT INTO 可以用来插入子查询 *********************************************************/

INSERT INTO COURSE(CNO,CNAME,CPNO,CCREDIT)
      SELECT '8',CNAME,CPNO,CCREDIT FROM  COURSE WHERE  CNO='2';