導出現有數據庫數據：

• mysqldump -u用戶名 -p密碼 數據庫名稱 >導出文件路徑 # 結構+數據
• mysqldump -u用戶名 -p密碼 -d 數據庫名稱 >導出文件路徑 # 結構

導入現有數據庫數據：

• mysqldump -uroot -p密碼 數據庫名稱 < 文件路徑

1.創建表
create table class(
	cid int auto_increment primary key,
	caption char(10)
)engine=innodb default charset=utf8;
insert into class(caption) values(‘三年二班‘),(‘一年三班‘),(‘三年一班‘);


create table student(
	sid int auto_increment primary key,
	sname char(10),
	gender char(10),
	class_id int,
	constraint fk_class foreign key (class_id) references class(cid)
)engine=innodb default charset=utf8;
insert into student(sname,gender,class_id) values(‘鋼彈‘,‘女‘,1),(‘鐵錘‘,‘女‘,2),(‘山炮‘,‘男‘,2);


create table teacher(
	tid int auto_increment primary key,
	tname char(10)
)engine=innodb default charset=utf8;
insert into teacher(tname) values(‘波多‘),(‘蒼空‘),(‘飯島‘);


create table course(
	cid int auto_increment primary key,
	cname char(10),
	tearch_id int,
	constraint fk_teacher foreign key (tearch_id) references teacher(tid)
)engine=innodb default charset=utf8;
insert into course(cname,tearch_id) values(‘生物‘,1),(‘體育‘,1),(‘物理‘,2);


create table score(
	sid int auto_increment primary key,
	student_id int,
	corse_id int,
	number int,
	unique score_index (student_id,corse_id),
	constraint fk_student foreign key (student_id) references student(sid),
	constraint fk_corse foreign key (corse_id) references course(cid)
)engine=innodb default charset=utf8;
insert into score(student_id,corse_id,number) values(1,1,60),(1,2,59),(2,2,100);

下面創建的表內容比較多，用於後面的練習題使用。

/*
 Navicat Premium Data Transfer

 Source Server         : localhost
 Source Server Type    : MySQL
 Source Server Version : 50624
 Source Host           : localhost
 Source Database       : sqlexam

 Target Server Type    : MySQL
 Target Server Version : 50624
 File Encoding         : utf
 
-8

 Date: 10/21/2016 06:46:46 AM
*/

SET NAMES utf8;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
--  Table structure for `class`
-- ----------------------------
DROP TABLE IF EXISTS `class`;
CREATE TABLE `class` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `caption` varchar(32) NOT NULL,
  PRIMARY KEY (`cid`)
) ENGINE
 
=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `class`
-- ----------------------------
BEGIN;
INSERT INTO `class` VALUES (‘1‘, ‘三年二班‘), (‘2‘, ‘三年三班‘), (‘3‘, ‘一年二班‘), (‘4‘, ‘二年九班‘);
COMMIT;

-- ----------------------------
--  Table structure for `course`
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `cname` varchar(32) NOT NULL,
  `teacher_id` int(11) NOT NULL,
  PRIMARY KEY (`cid`),
  KEY `fk_course_teacher` (`teacher_id`),
  CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `course`
-- ----------------------------
BEGIN;
INSERT INTO `course` VALUES (‘1‘, ‘生物‘, ‘1‘), (‘2‘, ‘物理‘, ‘2‘), (‘3‘, ‘體育‘, ‘3‘), (‘4‘, ‘美術‘, ‘2‘);
COMMIT;

-- ----------------------------
--  Table structure for `score`
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `student_id` int(11) NOT NULL,
  `course_id` int(11) NOT NULL,
  `num` int(11) NOT NULL,
  PRIMARY KEY (`sid`),
  KEY `fk_score_student` (`student_id`),
  KEY `fk_score_course` (`course_id`),
  CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`),
  CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`)
) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `score`
-- ----------------------------
BEGIN;
INSERT INTO `score` VALUES (‘1‘, ‘1‘, ‘1‘, ‘10‘), (‘2‘, ‘1‘, ‘2‘, ‘9‘), (‘5‘, ‘1‘, ‘4‘, ‘66‘), (‘6‘, ‘2‘, ‘1‘, ‘8‘), (‘8‘, ‘2‘, ‘3‘, ‘68‘), (‘9‘, ‘2‘, ‘4‘, ‘99‘), (‘10‘, ‘3‘, ‘1‘, ‘77‘), (‘11‘, ‘3‘, ‘2‘, ‘66‘), (‘12‘, ‘3‘, ‘3‘, ‘87‘), (‘13‘, ‘3‘, ‘4‘, ‘99‘), (‘14‘, ‘4‘, ‘1‘, ‘79‘), (‘15‘, ‘4‘, ‘2‘, ‘11‘), (‘16‘, ‘4‘, ‘3‘, ‘67‘), (‘17‘, ‘4‘, ‘4‘, ‘100‘), (‘18‘, ‘5‘, ‘1‘, ‘79‘), (‘19‘, ‘5‘, ‘2‘, ‘11‘), (‘20‘, ‘5‘, ‘3‘, ‘67‘), (‘21‘, ‘5‘, ‘4‘, ‘100‘), (‘22‘, ‘6‘, ‘1‘, ‘9‘), (‘23‘, ‘6‘, ‘2‘, ‘100‘), (‘24‘, ‘6‘, ‘3‘, ‘67‘), (‘25‘, ‘6‘, ‘4‘, ‘100‘), (‘26‘, ‘7‘, ‘1‘, ‘9‘), (‘27‘, ‘7‘, ‘2‘, ‘100‘), (‘28‘, ‘7‘, ‘3‘, ‘67‘), (‘29‘, ‘7‘, ‘4‘, ‘88‘), (‘30‘, ‘8‘, ‘1‘, ‘9‘), (‘31‘, ‘8‘, ‘2‘, ‘100‘), (‘32‘, ‘8‘, ‘3‘, ‘67‘), (‘33‘, ‘8‘, ‘4‘, ‘88‘), (‘34‘, ‘9‘, ‘1‘, ‘91‘), (‘35‘, ‘9‘, ‘2‘, ‘88‘), (‘36‘, ‘9‘, ‘3‘, ‘67‘), (‘37‘, ‘9‘, ‘4‘, ‘22‘), (‘38‘, ‘10‘, ‘1‘, ‘90‘), (‘39‘, ‘10‘, ‘2‘, ‘77‘), (‘40‘, ‘10‘, ‘3‘, ‘43‘), (‘41‘, ‘10‘, ‘4‘, ‘87‘), (‘42‘, ‘11‘, ‘1‘, ‘90‘), (‘43‘, ‘11‘, ‘2‘, ‘77‘), (‘44‘, ‘11‘, ‘3‘, ‘43‘), (‘45‘, ‘11‘, ‘4‘, ‘87‘), (‘46‘, ‘12‘, ‘1‘, ‘90‘), (‘47‘, ‘12‘, ‘2‘, ‘77‘), (‘48‘, ‘12‘, ‘3‘, ‘43‘), (‘49‘, ‘12‘, ‘4‘, ‘87‘), (‘52‘, ‘13‘, ‘3‘, ‘87‘);
COMMIT;

-- ----------------------------
--  Table structure for `student`
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `gender` char(1) NOT NULL,
  `class_id` int(11) NOT NULL,
  `sname` varchar(32) NOT NULL,
  PRIMARY KEY (`sid`),
  KEY `fk_class` (`class_id`),
  CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `student`
-- ----------------------------
BEGIN;
INSERT INTO `student` VALUES (‘1‘, ‘男‘, ‘1‘, ‘理解‘), (‘2‘, ‘女‘, ‘1‘, ‘鋼蛋‘), (‘3‘, ‘男‘, ‘1‘, ‘張三‘), (‘4‘, ‘男‘, ‘1‘, ‘張一‘), (‘5‘, ‘女‘, ‘1‘, ‘張二‘), (‘6‘, ‘男‘, ‘1‘, ‘張四‘), (‘7‘, ‘女‘, ‘2‘, ‘鐵錘‘), (‘8‘, ‘男‘, ‘2‘, ‘李三‘), (‘9‘, ‘男‘, ‘2‘, ‘李一‘), (‘10‘, ‘女‘, ‘2‘, ‘李二‘), (‘11‘, ‘男‘, ‘2‘, ‘李四‘), (‘12‘, ‘女‘, ‘3‘, ‘如花‘), (‘13‘, ‘男‘, ‘3‘, ‘劉三‘), (‘14‘, ‘男‘, ‘3‘, ‘劉一‘), (‘15‘, ‘女‘, ‘3‘, ‘劉二‘), (‘16‘, ‘男‘, ‘3‘, ‘劉四‘);
COMMIT;

-- ----------------------------
--  Table structure for `teacher`
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
  `tid` int(11) NOT NULL AUTO_INCREMENT,
  `tname` varchar(32) NOT NULL,
  PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `teacher`
-- ----------------------------
BEGIN;
INSERT INTO `teacher` VALUES (‘1‘, ‘張磊老師‘), (‘2‘, ‘李平老師‘), (‘3‘, ‘劉海燕老師‘), (‘4‘, ‘朱雲海老師‘), (‘5‘, ‘李傑老師‘);
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;

上述表均是在Navicat創建的。

2、查詢“生物”課程比“物理”課程成績高的所有學生的學號；
思路：
    獲取所有有生物課程的人（學號，成績） - 臨時表
    獲取所有有物理課程的人（學號，成績） - 臨時表
    根據【學號】連接兩個臨時表：
        學號  物理成績   生物成績
 
    然後再進行篩選
 
        select A.student_id,sw,ty from
 
        (select student_id,num as sw from score left join course on score.course_id = course.cid where course.cname = ‘生物‘) as A
 
        left join
 
        (select student_id,num  as ty from score left join course on score.course_id = course.cid where course.cname = ‘體育‘) as B
 
        on A.student_id = B.student_id where sw > if(isnull(ty),0,ty);
 
3、查詢平均成績大於60分的同學的學號和平均成績；
    思路：
        根據學生分組，使用avg獲取平均值，通過having對avg進行篩選
 
        select student_id,avg(num) from score group by student_id having avg(num) > 60
 
4、查詢所有同學的學號、姓名、選課數、總成績；
 
    select score.student_id,sum(score.num),count(score.student_id),student.sname
    from
        score left join student on score.student_id = student.sid  
    group by score.student_id
 
5、查詢姓“李”的老師的個數；
    select count(tid) from teacher where tname like ‘李%‘
 
    select count(1) from (select tid from teacher where tname like ‘李%‘) as B
 
6、查詢沒學過“葉平”老師課的同學的學號、姓名；
    思路：
        先查到“李平老師”老師教的所有課ID
        獲取選過課的所有學生ID
        學生表中篩選
    select * from student where sid not in (
        select DISTINCT student_id from score where score.course_id in (
            select cid from course left join teacher on course.teacher_id = teacher.tid where tname = ‘李平老師‘
        )
    )
 
7、查詢學過“001”並且也學過編號“002”課程的同學的學號、姓名；
    思路：
        先查到既選擇001又選擇002課程的所有同學
        根據學生進行分組，如果學生數量等於2表示，兩門均已選擇
 
    select student_id,sname from
 
    (select student_id,course_id from score where course_id = 1 or course_id = 2) as B
      
    left join student on B.student_id = student.sid group by student_id HAVING count(student_id) > 1
 
 
8、查詢學過“葉平”老師所教的所有課的同學的學號、姓名；
 
    同上，只不過將001和002變成 in (葉平老師的所有課)
 
9、查詢課程編號“002”的成績比課程編號“001”課程低的所有同學的學號、姓名；
    同第1題
 
 
10、查詢有課程成績小於60分的同學的學號、姓名；
         
    select sid,sname from student where sid in (
        select distinct student_id from score where num < 60
    )
 
11、查詢沒有學全所有課的同學的學號、姓名；
    思路：
        在分數表中根據學生進行分組，獲取每一個學生選課數量
        如果數量 == 總課程數量，表示已經選擇了所有課程
 
        select student_id,sname
        from score left join student on score.student_id = student.sid
        group by student_id HAVING count(course_id) = (select count(1) from course)
 
 
12、查詢至少有一門課與學號為“001”的同學所學相同的同學的學號和姓名；
    思路：
        獲取 001 同學選擇的所有課程
        獲取課程在其中的所有人以及所有課程
        根據學生篩選，獲取所有學生信息
        再與學生表連接，獲取姓名
 
        select student_id,sname, count(course_id)
        from score left join student on score.student_id = student.sid
        where student_id != 1 and course_id in (select course_id from score where student_id = 1) group by student_id
 
13、查詢至少學過學號為“001”同學所有課的其他同學學號和姓名；
        先找到和001的學過的所有人
        然後個數 ＝ 001所有學科     ＝＝》 其他人可能選擇的更多
 
        select student_id,sname, count(course_id)
        from score left join student on score.student_id = student.sid
        where student_id != 1 and course_id in (select course_id from score where student_id = 1) group by student_id having count(course_id) ＝ (select count(course_id) from score where student_id = 1)
 
14、查詢和“002”號的同學學習的課程完全相同的其他同學學號和姓名；
         
        個數相同
        002學過的也學過
 
        select student_id,sname from score left join student on score.student_id = student.sid where student_id in (
            select student_id from score  where student_id != 1 group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
        ) and course_id in (select course_id from score where student_id = 1) group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
 
 
15、刪除學習“葉平”老師課的score表記錄；
 
    delete from score where course_id in (
        select cid from course left join teacher on course.teacher_id = teacher.tid where teacher.name = ‘葉平‘
    )
 
16、向SC表中插入一些記錄，這些記錄要求符合以下條件：①沒有上過編號“002”課程的同學學號；②插入“002”號課程的平均成績；
    思路：
        由於insert 支持 
                inset into tb1(xx,xx) select x1,x2 from tb2;
        所有，獲取所有沒上過002課的所有人，獲取002的平均成績
 
    insert into score(student_id, course_id, num) select sid,2,(select avg(num) from score where course_id = 2)
    from student where sid not in (
        select student_id from score where course_id = 2
    )
     
17、按平均成績從低到高 顯示所有學生的“語文”、“數學”、“英語”三門的課程成績，按如下形式顯示： 學生ID,語文,數學,英語,有效課程數,有效平均分；
    select sc.student_id,
        (select num from score left join course on score.course_id = course.cid where course.cname = "生物" and score.student_id=sc.student_id) as sy,
        (select num from score left join course on score.course_id = course.cid where course.cname = "物理" and score.student_id=sc.student_id) as wl,
        (select num from score left join course on score.course_id = course.cid where course.cname = "體育" and score.student_id=sc.student_id) as ty,
        count(sc.course_id),
        avg(sc.num)
    from score as sc
    group by student_id desc        
 
18、查詢各科成績最高和最低的分：以如下形式顯示：課程ID，最高分，最低分；
     
    select course_id, max(num) as max_num, min(num) as min_num from score group by course_id;
 
19、按各科平均成績從低到高和及格率的百分數從高到低順序；
    思路：case when .. then
    select course_id, avg(num) as avgnum,sum(case when score.num > 60 then 1 else 0 END)/count(1)*100 as percent from score group by course_id order by avgnum asc,percent desc;
 
20、課程平均分從高到低顯示（現實任課老師）；
 
    select avg(if(isnull(score.num),0,score.num)),teacher.tname from course
    left join score on course.cid = score.course_id
    left join teacher on course.teacher_id = teacher.tid
 
    group by score.course_id
 
 
21、查詢各科成績前三名的記錄:(不考慮成績並列情況)
    select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
    (
    select
        sid,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 3,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.num <= T.first_num and score.num >= T.second_num
 
22、查詢每門課程被選修的學生數；
     
    select course_id, count(1) from score group by course_id;
 
23、查詢出只選修了一門課程的全部學生的學號和姓名；
    select student.sid, student.sname, count(1) from score
 
    left join student on score.student_id  = student.sid
 
     group by course_id having count(1) = 1
 
 
24、查詢男生、女生的人數；
    select * from
    (select count(1) as man from student where gender=‘男‘) as A ,
    (select count(1) as feman from student where gender=‘女‘) as B
 
25、查詢姓“張”的學生名單；
    select sname from student where sname like ‘張%‘;
 
26、查詢同名同姓學生名單，並統計同名人數；
 
    select sname,count(1) as count from student group by sname;
 
27、查詢每門課程的平均成績，結果按平均成績升序排列，平均成績相同時，按課程號降序排列；
    select course_id,avg(if(isnull(num), 0 ,num)) as avg from score group by course_id order by avg     asc,course_id desc;
 
28、查詢平均成績大於85的所有學生的學號、姓名和平均成績；
 
    select student_id,sname, avg(if(isnull(num), 0 ,num)) from score left join student on score.student_id = student.sid group by student_id;
 
29、查詢課程名稱為“數學”，且分數低於60的學生姓名和分數；
 
    select student.sname,score.num from score
    left join course on score.course_id = course.cid
    left join student on score.student_id = student.sid
    where score.num < 60 and course.cname = ‘生物‘
 
30、查詢課程編號為003且課程成績在80分以上的學生的學號和姓名；
    select * from score where score.student_id = 3 and score.num > 80
 
31、求選了課程的學生人數
 
    select count(distinct student_id) from score
 
    select count(c) from (
        select count(student_id) as c from score group by student_id) as A
 
32、查詢選修“楊艷”老師所授課程的學生中，成績最高的學生姓名及其成績；
     
    select sname,num from score
    left join student on score.student_id = student.sid
    where score.course_id in (select course.cid from course left join teacher on course.teacher_id = teacher.tid where tname=‘張磊老師‘) order by num desc limit 1;
 
33、查詢各個課程及相應的選修人數；
    select course.cname,count(1) from score
    left join course on score.course_id = course.cid
    group by course_id;
 
 
34、查詢不同課程但成績相同的學生的學號、課程號、學生成績；
    select DISTINCT s1.course_id,s2.course_id,s1.num,s2.num from score as s1, score as s2 where s1.num = s2.num and s1.course_id != s2.course_id;
 
35、查詢每門課程成績最好的前兩名；
 
    select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
    (
    select
        sid,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 1,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.num <= T.first_num and score.num >= T.second_num
 
36、檢索至少選修兩門課程的學生學號；
    select student_id from score group by student_id having count(student_id) > 1
 
37、查詢全部學生都選修的課程的課程號和課程名；
    select course_id,count(1) from score group by course_id having count(1) = (select count(1) from student);
 
38、查詢沒學過“葉平”老師講授的任一門課程的學生姓名；
    select student_id,student.sname from score
    left join student on score.student_id = student.sid
    where score.course_id not in (
        select cid from course left join teacher on course.teacher_id = teacher.tid where tname = ‘張磊老師‘
    )
    group by student_id
 
39、查詢兩門以上不及格課程的同學的學號及其平均成績；
 
    select student_id,count(1) from score where num < 60 group by student_id having count(1) > 2
 
40、檢索“004”課程分數小於60，按分數降序排列的同學學號；
    select student_id from score where num< 60 and course_id = 4 order by num desc;
 
41、刪除“002”同學的“001”課程的成績；
    delete from score where course_id = 1 and student_id = 2

MySQL練習題參考答案