加油,宝贝们,

细细品味,体会其中的原理, 首先要理解,然后是孰能生巧,ヾ(◍°∇°◍)ノ゙

个人提示: 要理解 一对多,  谁是主表,是建立外联的关键, 其次是 语法的熟练度(单词能掌握更好)

1.建立表关系:

请创建如下表,并创建相关约束

1 USE db1; 2 CREATE TABLE class( 3 cid INT AUTO_INCREMENT PRIMARY KEY, 4 caption VARCHAR(10) 5 ); 6 CREATE TABLE teacher( 7 tid INT AUTO_INCREMENT PRIMARY KEY, 8 tname VARCHAR(10) 9 );10 CREATE TABLE course(11 cid INT AUTO_INCREMENT PRIMARY KEY,12 cname VARCHAR(10),13 teach_id INT,14 CONSTRAINT fk_course_teacher FOREIGN KEY(teach_id) REFERENCES teacher(tid)15 );16 CREATE TABLE student(17 sid INT AUTO_INCREMENT PRIMARY KEY,18 sname VARCHAR(10),19 gender VARCHAR(10),20 class_id INT,21 CONSTRAINT fk_student_class FOREIGN KEY(class_id) REFERENCES class(cid)22 );23 CREATE TABLE score(24 sid INT AUTO_INCREMENT PRIMARY KEY,25 student_id INT,26 course_id INT,27 number INT,28 CONSTRAINT fk_score_student FOREIGN KEY(student_id) REFERENCES student(sid),29 CONSTRAINT fk_score_course FOREIGN KEY(course_id) REFERENCES course(cid)30 );

1 INSERT INTO class(caption) VALUES("三年二班"); 2 INSERT INTO class(caption) VALUES("一年三班"); 3 INSERT INTO class(caption) VALUES("三年一班"); 4 5 INSERT INTO teacher(tname) VALUES("波多"); 6 INSERT INTO teacher(tname) VALUES("苍空"); 7 INSERT INTO teacher(tname) VALUES("饭岛"); 8 9 INSERT INTO student(sname,gender,class_id) VALUES("钢蛋","女",1);10 INSERT INTO student(sname,gender,class_id) VALUES("铁锤","女",1);11 INSERT INTO student(sname,gender,class_id) VALUES("山炮","男",2);12 13 INSERT INTO course(cname,teach_id) VALUES("生物",1);14 INSERT INTO course(cname,teach_id) VALUES("体育",1);15 INSERT INTO course(cname,teach_id) VALUES("物理",2);16 17 INSERT INTO score(student_id,course_id,number) VALUES(1,1,60);18 INSERT INTO score(student_id,course_id,number) VALUES(1,2,59);19 INSERT INTO score(student_id,course_id,number) VALUES(2,2,100);

1 ALTER TABLE score ADD UNIQUE sco_que(student_id,course_id);2.操作练习:

1、自行创建测试数据

1 INSERT INTO student(sname,gender,class_id) VALUES("钢铁侠","男",4);2 -- Cannot add or update a child row: a foreign key constraint fails (`db1`.`student`, CONSTRAINT `fk_student_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`))2、查询“生物”课程比“物理”课程成绩高的所有学生的学号;

1 SELECT s1.student_id FROM (SELECT a.student_id,a.`number` FROM score a,course b 2 WHERE a.`course_id` = b.`cid` AND b.`cname` ="生物") s1 , (SELECT a.student_id,a.`number` FROM score a,course b 3 WHERE a.`course_id` = b.`cid` AND b.`cname`="体育") s24 WHERE s1.`student_id` = s2.student_id AND s1.number >s2.number3、查询平均成绩大于60分的同学的学号和平均成绩;

1 SELECT student_id,AVG(number)2 FROM score 3 GROUP BY student_id4 HAVING AVG(number) > 604、查询所有同学的学号、姓名、选课数、总成绩;

1 SELECT a.`sid`,a.`sname`,b.`cname`,c.`number`,c.`course_id`,a.`class_id` 2 FROM student a,course b,score c3 WHERE a.`sid` = c.`student_id` AND c.`course_id` = b.`cid`5、查询姓“李”的老师的个数;

1 SELECT count(*) as a from teacher where tname LIKE '李%'6、查询没学过“叶平”老师课的同学的学号、姓名;

1 SELECT a.sid,a.sname FROM student a,teacher b,course c2 WHERE a.class_id = c.cid and b.tid = c.teach_id AND b.tname != '叶平'7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名;

1 SELECT a.`student_id`,c.`sname` FROM score a , score b ,student c2 WHERE a.`student_id`=b.`student_id` AND a.`course_id` ='1' 3 AND b.`course_id`='2' AND c.`sid` = a.`student_id`8、查询学过“叶平”老师所教的所有课的同学的学号、姓名;

1 SELECT c.`sid`,c.`sname` FROM student c 2 LEFT JOIN score d ON c.`sid` = d.`student_id` 3 LEFT JOIN course b ON d.`course_id` = b.`cid` 4 LEFT JOIN teacher a ON a.`tid` = b.`teach_id` 5 WHERE a.`tname`='波多' 6 GROUP BY c.`sname` 7 HAVING COUNT(c.sname) 8 <(SELECT COUNT(*) FROM teacher a 9 LEFT JOIN course b ON a.`tid` = b.`teach_id`10 WHERE a.`tname`='波多')

9、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名;

1 SELECT s1.student_id FROM (SELECT a.student_id,a.`number` FROM score a,course b 2 WHERE a.`course_id` = b.`cid` AND b.`cid` ='2') s1 , (SELECT a.student_id,a.`number` FROM score a,course b 3 WHERE a.`course_id` = b.`cid` AND b.`cid`='1') s24 WHERE s1.`student_id` = s2.student_id AND s1.number >s2.number10、查询有课程成绩小于60分的同学的学号、姓名;

1 SELECT a.`sid`,a.`sname` FROM student a , score    b2 WHERE a.sid = b.student_id AND number < 6011、查询没有学全所有课的同学的学号、姓名;

1 SELECT a.`sid`,a.`sname` FROM student a 2 LEFT JOIN score b ON a.`sid` = b.`student_id`3 GROUP BY a.`sid`4 HAVING COUNT(b.`student_id`) < (SELECT COUNT(*) FROM course)12、查询至少有一门课与学号为“001”的同学所学相同的同学的学号和姓名;

1 SELECT a.`sid`,a.`sname` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`2 LEFT JOIN course c ON c.`cid` = b.`course_id`3 WHERE c.`cid` IN (4 SELECT cc.`cid` FROM student aa LEFT JOIN score bb ON aa.`sid` = bb.`student_id`5 LEFT JOIN course cc ON cc.`cid` = bb.`course_id` WHERE aa.`sid`='1'6 ) AND a.`sid` !='1'13、查询至少学过学号为“001”同学所选课程中任意一门课的其他同学学号和姓名;

SELECT a.`sid`,a.`sname` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`LEFT JOIN course c ON c.`cid` = b.`course_id`WHERE c.`cid` IN (SELECT cc.`cid` FROM student aa LEFT JOIN score bb ON aa.`sid` = bb.`student_id`LEFT JOIN course cc ON cc.`cid` = bb.`course_id` WHERE aa.`sid`='1') AND a.`sid` !='1'14、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名;

1 SELECT a.`sid`,a.`sname` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id` 2 LEFT JOIN course ac ON b.`course_id`=ac.`cid` 3 WHERE 4 ac.`cid` IN (SELECT c.`cid` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id` 5 LEFT JOIN course c ON b.`course_id`=c.`cid` WHERE a.`sid`='2') 6 AND a.`sid` != '2' 7 GROUP BY a.`sid`,a.`sname` 8 HAVING 9 (SELECT COUNT(ac.`cid`) AS countCid FROM student aa LEFT JOIN score b ON aa.`sid` = b.`student_id`10 LEFT JOIN course ac ON b.`course_id`=ac.`cid` WHERE aa.`sid`=a.`sid`)11 = (SELECT COUNT(c.`cid`) AS cc FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`12 LEFT JOIN course c ON b.`course_id`=c.`cid` WHERE a.`sid`='2')

15、删除学习“叶平”老师课的SC表记录;

1 DELETE FROM score WHERE course_id IN (2 SELECT a.`cid` FROM course a LEFT JOIN teacher b ON a.`teach_id`=b.`tid`3 WHERE b.`tname`='叶平'4 )16、向SC表中插入一些记录,这些记录要求符合以下条件:①没有上过编号“002”课程的同学学号;②插入“002”号课程的平均成绩; 17、按平均成绩从低到高显示所有学生的“语文”、“数学”、“英语”三门的课程成绩,按如下形式显示: 学生ID,语文,数学,英语,有效课程数,有效平均分;18、查询各科成绩最高和最低的分:以如下形式显示:课程ID,最高分,最低分;19、按各科平均成绩从低到高和及格率的百分数从高到低顺序;20、课程平均分从高到低显示(现实任课老师);21、查询各科成绩前三名的记录:(不考虑成绩并列情况) 22、查询每门课程被选修的学生数;23、查询出只选修了一门课程的全部学生的学号和姓名;24、查询男生、女生的人数;25、查询姓“张”的学生名单;26、查询同名同姓学生名单,并统计同名人数;27、查询每门课程的平均成绩,结果按平均成绩升序排列,平均成绩相同时,按课程号降序排列;28、查询平均成绩大于85的所有学生的学号、姓名和平均成绩;29、查询课程名称为“数学”,且分数低于60的学生姓名和分数;30、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名; 31、求选了课程的学生人数32、查询选修“杨艳”老师所授课程的学生中,成绩最高的学生姓名及其成绩;33、查询各个课程及相应的选修人数;34、查询不同课程但成绩相同的学生的学号、课程号、学生成绩;

35、查询每门课程成绩最好的前两名;

1 SELECT student_id FROM score 2 ORDER BY number DESC LIMIT 236、检索至少选修两门课程的学生学号;

1 SELECT a.`sid` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`2 GROUP BY a.`sid`3 HAVING COUNT(a.`sid`)>=237、查询全部学生都选修的课程的课程号和课程名;

1 SELECT DISTINCT c.`cid`,c.`cname` FROM student a 2 LEFT JOIN score b ON a.`sid` = b.`student_id`3 LEFT JOIN course c ON b.`course_id`=c.`cid`38、查询没学过“叶平”老师讲授的任一门课程的学生姓名;

1 SELECT a.`sname` FROM student a 2 LEFT JOIN score b ON a.`sid` = b.`student_id`3 LEFT JOIN course c ON c.`cid` = b.`course_id`4 WHERE c.`cid` NOT IN (5 SELECT cour.`cid` FROM teacher teac 6 LEFT JOIN course cour ON teac.`tid`=cour.`teach_id`7 WHERE teac.`tname` = '波多' 8 )

39、查询两门以上不及格课程的同学的学号及其平均成绩;

1 SELECT student_id,COUNT(sid) AS co,AVG(number)AS avgg FROM score 2 WHERE number < 60 3 GROUP BY student_id4 HAVING co >=240、检索“004”课程分数小于60,按分数降序排列的同学学号;

1 SELECT b.`sid`,b.`sname`,a.`number` FROM score a LEFT JOIN student b ON a.`student_id` = b.`sid`2 WHERE a.`course_id` = '4' AND a.`number` < '60'3 ORDER BY a.`number` DESC41、删除“002”同学的“001”课程的成绩;