总结：
一、单表查询的情况：
1.where.....group by .. Having count(..)
2.Group by haing min(..)条件and max(..)条件（查询最低分大于70，最高分小于90的Sno列）
二、两个表查询的情况：
1.select ....from t1 a join t2 b on a.cno=b.cno;
2.select ....from t1 a join t2 b on a.cno=b.cno where 具体的条件;
3.查询所有教师和同学的name、sex和birthday.
$sql= SELECT sname AS NAME, ssex AS SEX, sbirthday AS BIRTHDAY FROM student UNION SELECT tname AS NAME, tsex AS SEX, tbirthday AS BIRTHDAY FROM teacher;
三、三个表以上查询
1.select ....from t1 a join（t2 b,t3 c,....）on a.cno=b.cno and b.sno=c.sno;
2.select ....from t1 a join（t2 b,t3 c,....）on a.cno=b.cno and b.sno=c.sno group by ..having count(..) 条件
3.select ....from t1 a join（t2 b,t3 c,....）on a.cno=b.cno and b.sno=c.sno where
具体的条件
现在将题目和答案分享一下。我使用的是MYSQL 5.0，但是绝大部分都是标准SQL。
表结构：
CREATE TABLE student
(SNO VARCHAR(3) NOT NULL,
SNAME VARCHAR(4) NOT NULL,
SSEX VARCHAR(2) NOT NULL,
SBIRTHDAY DATETIME,
CLASS VARCHAR(5))
go
CREATE TABLE course
(CNO VARCHAR(5) NOT NULL,
CNAME VARCHAR(10) NOT NULL,
TNO VARCHAR(10) NOT NULL)
go
CREATE TABLE score
(SNO VARCHAR(3) NOT NULL,
CNO VARCHAR(5) NOT NULL,
DEGREE NUMERIC(10, 1) NOT NULL);
go
CREATE TABLE teacher
(TNO VARCHAR(3) NOT NULL,
TNAME VARCHAR(4) NOT NULL, TSEX VARCHAR(2) NOT NULL,
TBIRTHDAY DATETIME NOT NULL, PROF VARCHAR(6),
DEPART VARCHAR(10) NOT NULL)
INSERT INTO student (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (108 ,'曾华'
,'男' ,'1977-09-01',95033);
INSERT INTO student (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (105 ,'匡明'
,'男' ,'1975-10-02',95031);
INSERT INTO student (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (107 ,'王丽'
,'女' ,'1976-01-23',95033);
INSERT INTO student (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (101 ,'李军'
,'男' ,'1976-02-20',95033);
INSERT INTO student (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (109 ,'王芳'
,'女' ,'1975-02-10',95031);
INSERT INTO student (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (103 ,'陆君'
,'男' ,'1974-06-03',95031);
GO
INSERT INTO course(CNO,CNAME,TNO)VALUES ('3-105' ,'计算机导论',825);
INSERT INTO course(CNO,CNAME,TNO)VALUES ('3-245' ,'操作系统' ,804);
INSERT INTO course(CNO,CNAME,TNO)VALUES ('6-166' ,'数据电路' ,856);
INSERT INTO course(CNO,CNAME,TNO)VALUES ('9-888' ,'高等数学' ,100);
GO
INSERT INTO score(SNO,CNO,DEGREE)VALUES (103,'3-245',86);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (105,'3-245',75);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (109,'3-245',68);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (103,'3-105',92);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (105,'3-105',88);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (109,'3-105',76);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (101,'3-105',64);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (107,'3-105',91);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (108,'3-105',78);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (101,'6-166',85);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (107,'6-106',79);
INSERT INTO score(SNO,CNO,DEGREE)VALUES (108,'6-166',81);
GO
INSERT INTO teacher(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART)
VALUES (804,'李诚','男','1958-12-02','副教授','计算机系');
INSERT INTO teacher(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART)
VALUES (856,'张旭','男','1969-03-12','讲师','电子工程系');
INSERT INTO teacher(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART)
VALUES (825,'王萍','女','1972-05-05','助教','计算机系');
INSERT INTO teacher(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART)
VALUES (831,'刘冰','女','1977-08-14','助教','电子工程系');
题目：
单表操作
1、 查询Student表中的所有记录的Sname、Ssex和Class列。
$Sql=select ssex,sname,class from student;
2、 查询教师所有的单位即不重复的Depart列。
$sql=select distinct depart from teacher;
3、 查询Student表的所有记录。
$sql=select*from student
4、 查询Score表中成绩在60到80之间的所有记录。（between .and .）
$sql=select*from score where degree between 60 and 80;
5、 查询Score表中成绩为85，86或88的记录。(in)
$sql=select*from score where degree in(85,86,88);
6、 查询Student表中“95031”班或性别为“女”的同学记录。(or)
$sql=select*from student where class='95031' or ssex='女';
7、 以Class降序查询Student表的所有记录。(order by desc/asc)
$sql=select*from student order by class desc;
8、 以Cno升序、Degree降序查询Score表的所有记录。(order by desc,asc)
$sql=select*from score order by cno asc,degree desc;
9、 查询“95031”班的学生人数。(count(*))
$sql=select count(*) as a from student where class='95031';
10、 查询Score表中的最高分的学生学号和课程号。(子查询、max(..))
$sql=select sno,cno from score where degree=(select max(degree) from score);
11、 查询‘3-105’号课程的平均分。(avg(..))
$sql=select avg(degree) from score where cno='3-105';
12、 ※查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。
$sql=select avg(degree),cno from score where cno like '3%' group by cno having count(sno)>= 5;
13、 ※查询最低分大于70，最高分小于90的Sno列。()
$sql=select sno from score group by sno having min(degree)>70 and max(degree)<90;
两个表查询：
14、 查询所有学生的Sname、Cno和Degree列。
$sql=select a.sname,b.cno,b.degree from student as a join score as b on a.sno=b.sno;
15、 查询所有学生的Sno、Cname和Degree列。
$sql=select a.cname,b.sno,b.degree from course as a join score as b on a.cno=b.cno;
（三表查询）
16、 ※查询所有学生的Sname、Cname和Degree列。
$sql=select a.sname,b.degree,c.cname from student as a join(score b,course c) on a.sno=b.sno and b.cno=c.cno;
17、 ※查询“95033”班所选课程的平均分。
$sql=select avg(a.degree) from score a join student b on a.sno=b.sno where b.class='95033';
18、 假设使用如下命令建立了一个grade表：
create table grade(low number(3,0),upp number(3),rank char(1));
insert into grade values(90,100,’A’);
insert into grade values(80,89,’B’);
insert into grade values(70,79,’C’);
insert into grade values(60,69,’D’);
insert into grade values(0,59,’E’);
commit;
现查询所有同学的Sno、Cno和rank列。
$sql=select a.sno,a.cno,b.rank from score a,grade b where a.degree between b.low and b.upp order by rank;
单表操作
19、查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。
① $sql=select*from score where cno='3-105' and degree>(select max(degree) from score where sno='109');
②select a.*from score a join score b where a.cno='3-105' and a.degree>b.degree and b.sno='109' and b.cno='3-105';
③ select a.*from score a where a.cno='3-105' and a.degree>all(select b.degree from score b where b.sno ='109' and b.cno='3-105');
20、※查询score中选学一门以上课程的同学中分数为非最高分成绩的记录。
$sql= select*from score s where degree<(select max(degree) from score) group by sno having count(sno)>1 order by degree;
21、查询成绩高于学号为“109”、课程号为“3-105”的成绩的所有记录。
① select*from score where cno='3-105' and degree>(select max(degree) from score where sno='109');
②select a.*from score a where a.cno='3-105' and a.degree>all(select b.degree from score b where b.sno ='109' and b.cno='3-105');
22、查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。
$sql=SELECT SNO,SNAME,SBIRTHDAY FROM STUDENT WHERE YEAR(SBIRTHDAY)=(SELECT YEAR(SBIRTHDAY)
FROM STUDENT WHERE SNO='108');
ORACLE:select x.cno,x.Sno,x.degree from score x,score y where x.degree>y.degree and
y.sno='109'and y.cno='3-105'; select cno,sno,degree from score where degree >(select degree from score where sno='109'
and cno='3-105')
（三表查询）
23、查询“张旭“教师任课的学生成绩。
① Sql=”select a.degree,a.sno from score a join(course b,teacher c) on b.tno=c.tno and a.cno=b.cno where c.tname='张旭';
”;
② 另一种解法：sql=”select cno,sno,degree from score where cno=(select x.cno from course x,teacher y where x.tno=y.tno and y.tname='张旭');”;
24、查询选修某课程的同学人数多于5人的教师姓名。
$sql=” select a.tname from teacher a join(course b,score c) on a.tno=b.tno and b.cno=c.cno group by c.cno having count(c.cno)>5;”;
25、查询95033班和95031班全体学生的记录。
单表操作
26、查询存在有85分以上成绩的课程Cno.
$sql=”select cno from score group by cno having max(degree)>85”;
（三表查询）
27、查询出“计算机系“教师所教课程的成绩表。
SELECT A.* FROM SCORE A JOIN (TEACHER B,COURSE C) ON A.CNO=C.CNO AND B.TNO=C.TNO WHERE B.DEPART='计算机系'; 另一种解法：SELECT * from score where cno in (select a.cno from course a join teacher b on
a.tno=b.tno and b.depart='计算机系'); 此时2略好于1，在多连接的境况下性能会迅速下降
单表操作
28、查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
$sql=’select tname,prof from teacher where depart='计算机系' and prof not in (select prof from teacher where depart='电子工程系')’;
29、查询选修编号为“3-105“课程且成绩至少高于选修编号为“3-245”的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。
$sql=’ select*from score where cno='3-105' and degree>any(select degree from score where cno='3-245') order by degree desc’;
30、查询选修编号为“3-105”且成绩高于选修编号为“3-245”课程的同学的Cno、Sno和Degree.
①$sql=’select*from score where cno='3-105' and degree>(select max(degree) from score where cno='3-245') order by degree desc’;
②$sql=’ select*from score where cno='3-105' and degree>all(select degree from score where cno='3-245') order by degree desc’;
两个表操作
31、查询所有教师和同学的name、sex和birthday.
$sql= SELECT sname AS NAME, ssex AS SEX, sbirthday AS BIRTHDAY FROM student UNION SELECT tname AS NAME, tsex AS SEX, tbirthday AS BIRTHDAY FROM teacher;
32、查询所有“女”教师和“女”同学的name、sex和birthday.
SELECT SNAME AS NAME, SSEX AS SEX, SBIRTHDAY AS BIRTHDAY FROM STUDENT WHERE SSEX='女' UNION SELECT TNAME AS NAME, TSEX AS SEX, TBIRTHDAY AS BIRTHDAY FROM TEACHER WHERE TSEX='女';
33、查询成绩比该课程平均成绩低的同学的成绩表。
$sql=’.SELECT A.* FROM SCORE A WHERE DEGREE<(SELECT AVG(DEGREE) FROM SCORE B WHERE A.CNO=B.CNO)’;须注意********此题
34、查询所有任课教师的Tname和Depart.
$sql=’ select a.tname,a.depart from teacher a left join course b using(tno) where isnull(b.tno);’;
35 查询所有未讲课的教师的Tname和Depart.
解法一：$sql=’ select a.tname,a.depart from teacher a left join course b using(tno) where isnull(b.tno)’;
(B解法二：select tname,depart from teacher a where not exists (select * from course b where a.tno=b.tno); 解法三：SELECT TNAME,DEPART FROM TEACHER WHERE TNO NOT IN (SELECT TNO FROM COURSE); NOT IN的方法效率最差，其余两种差不多
36、查询至少有2名男生的班号。
$sql=’SELECT CLASS FROM STUDENT A WHERE SSEX='男' GROUP BY CLASS HAVING COUNT(SSEX)>1’;
37、查询Student表中不姓“王”的同学记录。
$sql=’ select*from student where sname not like '王%'’;
38、查询Student表中每个学生的姓名和年龄。
$sql=’select sname,(YEAR(NOW())-YEAR(SBIRTHDAY)) AS AGE from student’;
39、查询Student表中最大和最小的Sbirthday日期值。
$sql=’select sname,sbirthday as THEMAX from student where sbirthday =(select min(SBIRTHDAY) from student) union select sname,sbirthday as THEMIN from student where sbirthday =(select max(SBIRTHDAY) from student);’;
40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
SELECT CLASS,(YEAR(NOW())-YEAR(SBIRTHDAY)) AS AGE FROM STUDENT ORDER BY CLASS DESC,AGE
DESC;
41、查询“男”教师及其所上的课程。
$sql=select a.cname,b.tname from course a join teacher b on a.tno=b.tno where b.tsex='男';
42、查询最高分同学的Sno、Cno和Degree列。
$sq=select*from score where degree=(select max(degree) from score);
43、查询和“李军”同性别的所有同学的Sname.
$sql=select sname from student where ssex=(select ssex from student where sname='李军');
44、查询和“李军”同性别并同班的同学Sname.
$sql=select sname from student a where ssex=(select ssex from student b where sname='李军')and class=(select class from student c where sname='李军');
45、查询所有选修“计算机导论”课程的“男”同学的成绩表
$sql=select * from score where sno in(select sno from student where ssex='男') and cno=(select cno from course where cname='计算机导论');