SQL高级查询
t_student(sid,sname,sage,ssex) 学生表
t_course(cid,cname,tid) 课程表
t_score( scid,sid,cid,grade) 成绩表
t_teacher(tid,tname) 教师表
CREATE TABLE `t_student` ( `sid` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键', `sname` varchar(16) NOT NULL COMMENT '学生姓名', `sage` int(11) DEFAULT NULL COMMENT '年龄', `sex` char(1) DEFAULT NULL COMMENT '性别（0：女，1：男）', PRIMARY KEY (`sid`) ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8
-- ----------------------------
-- Records of t_student
-- ----------------------------
INSERT INTO t_student VALUES ('1', 'Smile', '22', '1');
INSERT INTO t_student VALUES ('2', 'Somnus', '20', '0');
INSERT INTO t_student VALUES ('3', 'Smart', '22', '1');
INSERT INTO t_student VALUES ('4', 'Storm', '24', '0');
INSERT INTO t_student VALUES ('5', 'Simple', '23', '0');
INSERT INTO t_student VALUES ('6', 'Storm', '22', '0');
CREATE TABLE `t_course` ( `cid` int(11) NOT NULL AUTO_INCREMENT, `cname` varchar(32) NOT NULL COMMENT '课程名字', `tid` int(11) DEFAULT NULL COMMENT '外键-教师ID', PRIMARY KEY (`cid`), KEY `fk_book` (`tid`), CONSTRAINT `fk_book` FOREIGN KEY (`tid`) REFERENCES `t_teacher` (`tid`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
-- ----------------------------
-- Records of t_course
-- ----------------------------
INSERT INTO t_course VALUES ('1', '企业管理', '1');
INSERT INTO t_course VALUES ('2', '马克思', '2');
INSERT INTO t_course VALUES ('3', 'UML', '3');
INSERT INTO t_course VALUES ('4', '数据库', '4');
INSERT INTO t_course VALUES ('5', 'JAVA', '5');
CREATE TABLE `t_score` ( `sid` int(11) NOT NULL DEFAULT '0' COMMENT '学生ID', `cid` int(11) NOT NULL DEFAULT '0' COMMENT '课程ID', `grade` int(3) DEFAULT NULL COMMENT '成绩', PRIMARY KEY (`sid`,`cid`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
-- ----------------------------
-- Records of t_score
-- ----------------------------
INSERT INTO t_score VALUES ('1', '1', '78');
INSERT INTO t_score VALUES ('1', '2', '51');
INSERT INTO t_score VALUES ('1', '3', '48');
INSERT INTO t_score VALUES ('2', '1', '89');
INSERT INTO t_score VALUES ('2', '2', '97');
INSERT INTO t_score VALUES ('2', '3', '77');
INSERT INTO t_score VALUES ('2', '4', '99');
INSERT INTO t_score VALUES ('2', '5', '83');
INSERT INTO t_score VALUES ('3', '2', '67');
INSERT INTO t_score VALUES ('3', '3', '88');
INSERT INTO t_score VALUES ('3', '4', '89');
INSERT INTO t_score VALUES ('4', '1', '56');
INSERT INTO t_score VALUES ('4', '2', '36');
INSERT INTO t_score VALUES ('4', '4', '56');
INSERT INTO t_score VALUES ('4', '5', '47');
INSERT INTO t_score VALUES ('5', '2', '78');
INSERT INTO t_score VALUES ('5', '3', '72');
INSERT INTO t_score VALUES ('5', '4', '58');
INSERT INTO t_score VALUES ('6', '1', '55');
CREATE TABLE `t_teacher` ( `tid` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键ID', `tname` varchar(16) DEFAULT NULL COMMENT '教师名', PRIMARY KEY (`tid`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
-- ----------------------------
-- Records of t_teacher
-- ----------------------------
INSERT INTO t_teacher VALUES ('1', '叶平');
INSERT INTO t_teacher VALUES ('2', 'teacher2');
INSERT INTO t_teacher VALUES ('3', 'teacher3');
INSERT INTO t_teacher VALUES ('4', 'teacher4');
INSERT INTO t_teacher VALUES ('5', 'teacher5');
问题：
1、查询“1”课程比“2”课程成绩高的所有学生的学号；
select t1.sid from
(select sid,grade from t_score where cid = '1') t1,
(select sid,grade from t_score where cid = '2') t2
where t1.grade >t2.grade and t1.sid = t2.sid;
----------------------------------------------------------------------------------------------
select t2.sid,t2.ca,t2.cb(
select t1.sid,sum(t1.ca) ca,sum(t1.cb) cb
from
(
select sid,
CASE WHEN cid = '1' THEN grade ELSE 0 END ca,
CASE WHEN cid = '2' THEN grade ELSE 0 END cb
from t_score
)t1
GROUP BY sid
)t2
where t2.ca > t2.cb
2、查询平均成绩大于60分的同学的学号和平均成绩；
select sid,avg(grade ) from t_score
group by sid
having avg(grade ) >60;
3、查询所有同学的学号、姓名、选课数、总成绩；
select t1.sid,t1.sname,count(t2.cid),sum(grade ) from t_student t1
left join t_score t2
on t1.sid = t2.sid
group by t1.sid,t1.sname;
4、查询姓“李”的老师的个数；
select count(distinct(tname)) from t_teacher where tname like '李%';
5、查询没学过“叶平”老师课的同学的学号、姓名；
select sid, sname from t_student
where sid not in
(
select distinct(t1.sid) from t_score t1,t_course t2,t_teacher t3
where t1.cid = t2.cid and t3.tid = t2.tid and t3.tname = '叶平'
);
6、查询学过“1”并且也学过编号“2”课程的同学的学号、姓名；
select t0.sid,t0.sname from t_student t0, t_score t1
where t0.sid = t1.sid and t1.cid = '1'
and exists
(
select * from t_score t2 where t2.sid = t1.sid and t2.cid = '2'
);
7、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
select sid,sname from t_student
where sid in
(
select sid from t_score t1 ,t_course t2,t_teacher t3
where t1.cid=t2.cid
and t3.tid=t2.tid
and t3.tname = '叶平'
group by sid
having count(t1.cid)=(
select count(cid) from t_course t1,t_teacher t2
where t2.tid=t1.tid and t2.tname = '叶平'
)
);
8、查询“1”课程比“2”课程成绩高的所有同学的学号、姓名；
(
select t1.sid,t1.sname,t2.grade ,
(
select grade from t_score t3 where t3.sid = t1.sid and t3.cid = '2'
) grade2
from t_student t1, t_score t2 where t1.sid = t2.sid and t2.cid = '1'
) tt
where grade2 < grade ;
9、查询所有课程成绩小于60分的同学的学号、姓名；
select sid,sname from t_student
where sid not in
(
select t1.sid from t_student t1, t_score t2
where t1.sid = t2.sid and t2.grade >60
);
10、查询没有学全所有课的同学的学号、姓名；
select t1.sid,t1.sname from t_student t1, t_score t2
where t1.sid = t2.sid
group by t1.sid,t1.sname
having count(t2.cid) < (select count(cid) from t_course);
14、查询和“3”号的同学学习的课程完全相同的其他同学学号和姓名；
select sid from t_score
where cid in (select cid from t_score where sid = '3')
group by sid
having count(*)=(select count(*) from t_score where sid = '3');
15、删除学习“叶平”老师课的 t_score表记录；
delect t_score from t_course t1 ,t_teacher t2
Where t1.cid = t2.cid
and t1.tid = t2.tid
and t2.tname = '叶平';
16、向 t_score表中插入一些记录，这些记录要求符合以下条件：没有上过编号“3”课程的同学学号、2 号课程的平均成绩；
insert t_score
select sid,'2',(Select avg(grade ) from t_score where cid = '2')
from t_student
where sid not in (Select sid from t_score where cid = '2');
17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示： 学生ID,,数据库,企业管理,英语,有效课程数,有效平均分
SELECT sid as 学生ID,
(SELECT grade FROM t_score WHERE sid=t.sid AND cid='4') AS 数据库,
(SELECT grade FROM t_score WHERE sid=t.sid AND cid='1') AS 企业管理,
(SELECT grade FROM t_score WHERE sid=t.sid AND cid='5') AS JAVA,
COUNT(*) AS 有效课程数,
AVG(t.grade ) AS 平均成绩
FROM t_score AS t
GROUP BY sid
ORDER BY avg(t.grade )
21、查询不同老师所教不同课程平均分从高到低显示
SELECT max(t3.tid) AS 教师ID,MAX(t3.tname) AS 教师姓名,
T2.cid AS 课程ID,MAX(t2.cname) AS 课程名称,AVG(grade ) AS 平均成绩
FROM t_score AS t1,t_course AS t2 ,t_teacher AS t3
where t1.cid = t2.cid and t2.tid = t3.tid
GROUP BY t2.cid
ORDER BY AVG(grade ) DESC ;
23、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]
SELECT t1.cid as 课程ID, t2.cname as 课程名称,
SUM(CASE WHEN t1.grade BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 - 85],
SUM(CASE WHEN t1.grade BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 - 70],
SUM(CASE WHEN t1.grade BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 - 60],
SUM(CASE WHEN t1.grade < 60 THEN 1 ELSE 0 END) AS [60 -]
FROM t_score t1,t_course t2 where t1.cid = t2.cid
GROUP BY t1.cid,t2.cname;
24、查询学生平均成绩及其名次
SELECT
1+(
SELECT COUNT( distinct avggrade )
FROM (
SELECT sid,AVG(grade ) AS avggrade FROM t_score GROUP BY sid
) AS T1 WHERE avggrade > T2.avggrade ) as 名次,
sid as 学生学号,
avggrade
FROM (
SELECT sid,AVG(grade )as avggrade FROM t_score GROUP BY sid
) AS T2
ORDER BY avggrade desc;
26、查询每门课程被选修的学生数
select cid,count(sid) from t_score group by cid;
27、查询出只选修了一门课程的全部学生的学号和姓名
select t1.sid,t2.sname,count(t1.cid) AS 选课数 from t_score t1,t_student t2
where t1.sid=t2.sid
group by t1.sid ,t2.sname
having count(t1.cid)=1;
28、查询男生、女生人数
Select count(sex) as 男生人数 from t_student group by sex having sex='1';
Select count(sex) as 女生人数 from t_student group by sex having sex='0';
30、查询同名同性学生名单，并统计同名人数
select sname,count(*) from t_student group by sname having count(*)>1;
32、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
select cid,Avg(grade ) from t_score group by cid order by Avg(grade ),cid DESC
33、查询平均成绩大于85的所有学生的学号、姓名和平均成绩
select t1.sname, t2.sid ,avg(t2.grade ) from t_student t1, t_score t2
where t1.sid=t2.sid group by t2.sid,t1.sname
having avg(t2.grade )>85;
34、查询课程名称为“数据库”，且分数低于60的学生姓名和分数
Select t1.sname,ifnull(t2.grade ,0) from t_student t1, t_score t2,t_course t3
where t2.sid = t1.sid and t2.cid = t3.cid
and t3.cname='数据库'and t2.grade <60;
35、查询所有学生的选课情况；
SELECT t1.sid, t1.cid,t2.sname,t3.cname FROM t_score t1,t_student t2,t_course t3
where t1.sid = t2.sid and t1.cid = t3.cid ;
36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；
SELECT distinct t1.sid,t1.sname,t2.cid, t2.grade FROM t_student t1, t_score t2
WHERE t2.grade >=70 AND t2.sid = t1.sid;
37、查询不及格的课程，并按课程号从大到小排列
select cid from t_score where grade < 60 order by cid ;
38、查询课程编号为3且课程成绩在80分以上的学生的学号和姓名；
select t1.sid,t2.sname from t_score t1,t_student t2
where t1.sid = t2.sid and t1.grade > 80 and t1.cid = '3';
40、查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩
select t1.sname,t2.grade from t_student t1, t_score t2,t_course t3,t_teacher t4
where t1.sid = t2.sid
and t2.cid = t3.cid
and t3.tid = t4.tid
and t4.Tname = '叶平'
and t2.grade = (select max(grade )from t_score where cid=t3.cid );
42、查询不同课程成绩相同的学生的学号、课程号、学生成绩
select distinct t1.sid,t2.grade from t_score t1 , t_score t2
where t1.grade = t2.grade and t1.cid <>t2.cid ;
44、统计每门课程的学生选修人数（超过10人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，查询结果按人数降序排列，若人数相同，按课程号升序排列
select cid as 课程号,count(*) as 人数 from t_score
group by cid
order by count(*) desc,cid
45、检索至少选修两门课程的学生学号
select sid from t_score group by sid having count(*) >= 2
46、查询全部学生都选修的课程的课程号和课程名
select cid,cname from t_course where cid in (select cid from t_score group by cid)
47、查询没学过“叶平”老师讲授的任一门课程的学生姓名
select sname from t_student
where sid not in (
select sid from t_course t1,t_teacher t2, t_score t3
where t1.tid = t2.tid
and t3.cid =t1.cid
and t2.tname = '叶平'
);
48、查询两门以上不及格课程的同学的学号及其平均成绩
select sid,avg(ifnull(grade ,0)) from t_score
where sid in (
select sid from t_score
where grade <60 group by sid having count(*)>2
)
group by sid;
49、检索“4”课程分数小于60，按分数降序排列的同学学号
select sid from t_score where cid='4'and grade <60 order by grade desc;