1. 在表中插入符合主键
[sql]
/*成绩表*/
CREATE
TABLE
SC
(
Sid
INT
REFERENCES
Student(Sid),
/*学生学号*/
Cid
INT
REFERENCES
Course(Cid),
/*课程编号*/
Score
INT
NOT
NULL
,
/*课程分数*/
PRIMARY
KEY
(Sid,Cid)
/*将学生学号和课程编号设为复合主键*/
)
2. 查询各科成绩最高分，最低分以及平均分
[sql]
SELECT
c.Cname,
MAX
(s.Score)
AS
Max
,
MIN
(s.Score)
AS
Min
,
AVG
(s.Score)
AS
Average
FROM
Course c
JOIN
SC s
ON
c.Cid = s.Cid
GROUP
BY
c.Cname
/*此处应注意，若不按照c.Cname进行分组，SQL语句会报错，c.Cname在SELECT语句中不合法，因为它
并未出现在聚合函数中也没有出现在GROUP BY语句中*/
3. 查询平均成绩大于80分的学生姓名以及平均成绩
[sql]
SELECT
Sname,
AVG
(Score)
AS
Average
FROM
Student
JOIN
SC
ON
Student.Sid=SC.Sid
GROUP
BY
Sname
HAVING
AVG
(Score)>80
/*以聚合函数为条件进行删选只能在HAVING语句中进行，WHERE语句不支持聚合函数*/
4. 查询各学生都选了多少门课
[sql]
SELECT
Sname,
COUNT
(Cid)
AS
TOTAL_COURSE
FROM
Student
LEFT
JOIN
SC
ON
Student.Sid=SC.Sid
GROUP
BY
Sname
/*使用LEFT JOIN可以将一门课也没有选的学生也查询出来，
若不加LEFT查不出DAISY和SHERRY*/
5. 查询没有选JANE老师课的学生信息
[sql]
SELECT
s.Sid,s.Sname,s.Sage,s.Sage
FROM
Student s
WHERE
s.Sid
NOT
IN
(
SELECT
s.Sid
FROM
SC s
JOIN
Course c
ON
s.Cid=c.Cid
JOIN
Teacher t
ON
c.Tid=t.Tid
WHERE
t.Tname=
'JANE'
)
/*子查询中查询出所有选择JANE老师课的学生学号，
主查询去查询在学生表中但不在子查询结果集中的学生信息*/
6. 查询既选择了COMPUTER课程，又选择了MATH课程的学生信息
[sql]
SELECT
s.Sid,s.Sname,s.Sage,s.Ssex
FROM
STUDENT s
JOIN
SC ss
ON
s.Sid=ss.Sid
JOIN
Course c
ON
ss.Cid=c.Cid
WHERE
c.Cname=
'COMPUTER'
INTERSECT
SELECT
s.Sid,s.Sname,s.Sage,s.Ssex
FROM
STUDENT s
JOIN
SC ss
ON
s.Sid=ss.Sid
JOIN
Course c
ON
ss.Cid=c.Cid
WHERE
c.Cname=
'MATH'
/*第一个查询查询出选择COMPUTER课程的学生信息，
第二个查询查询出选择MATH课程的学生信息，
用INTERSECT关键字取交集*/
7. 查询COMPUTER课程比MATH课程分数高的学生学号
[sql]
SELECT
a.Sid
FROM
(
SELECT
s.Sid,s.Score
FROM
SC s
JOIN
Course c
ON
s.Cid=c.Cid
WHERE
c.Cname=
'COMPUTER'
) a
JOIN
(
SELECT
s.Sid,s.Score
FROM
SC s
JOIN
Course c
ON
s.Cid=c.Cid
WHERE
c.Cname=
'MATH'
) b
ON
a.Sid=b.Sid
WHERE
a.Score>b.Score
/*将选了COMPUTER课的学生学号和成绩和选了MATH课的学生学号和成绩连接
WHERE语句限制COMPUTER课的成绩高于MATH课*/
8. 查询和JOHN选的课相同的学生信息
[sql]
SELECT
Student.Sname
FROM
Student
JOIN
SC
ON
Student.Sid=SC.Sid
WHERE
SC.Cid
IN
(
SELECT
SC.Cid
FROM
SC
JOIN
Student
ON
SC.Sid=Student.Sid
WHERE
Student.Sname=
'JOHN'
)
/*查询选了的课JOHN也都选了的学生的姓名*/
AND
Student.Sname<>
'JOHN'
/*限制该学生不能是JOHN本人*/
GROUP
BY
Student.Sname
HAVING
COUNT
(SC.Cid)=
(
SELECT
COUNT
(*)
FROM
SC
JOIN
Student
ON
SC.Sid=Student.Sid
WHERE
Student.Sname=
'JOHN'
)
/*该学生选的课程总数与JOHN选的课程总数相同*/
9. 按总分为学生排名，总分相同名次相同
[sql]
SELECT
RANK() OVER (
ORDER
BY
SUM
(ss.Score)
DESC
)
AS
Rank, s.Sname,
ISNULL
(
SUM
(ss.Score),0)
FROM
Student s
LEFT
JOIN
SC ss
ON
s.Sid = ss.Sid
GROUP
BY
s.Sname
ORDER
BY
SUM
(ss.Score)
DESC
/*RANK()是SQL Server的一个built-in函数，语法为
RANK() OVER ( [ partition_by_clause ] order_by_clause ).*/
10. 查询总分在100至200之间的学生姓名及总分
[sql]
SELECT
s.Sname,
SUM
(ss.Score)
FROM
Student s
JOIN
SC ss
ON
s.Sid=ss.Sid
GROUP
BY
s.Sname
HAVING
SUM
(ss.Score)
BETWEEN
100
AND
200
11. 查询总分第六到十名的学生姓名以及总分
[sql]
SELECT
*
FROM
(
SELECT
TOP
(5) *
FROM
(
SELECT
TOP
(10) SC.Sid,
SUM
(SC.Score)
AS
SUM
FROM
SC
GROUP
BY
SC.Sid
ORDER
BY
SUM
(SC.Score)) a
ORDER
BY
a.
SUM
) b
ORDER
BY
b.
SUM
DESC
/*SELECT TOP(10) SC.Sid,SUM(SC.Score) AS SUM FROM SC GROUP BY SC.Sid ORDER BY SUM(SC.Score)查询出总分前十名
SELECT TOP(5) FROM (...) a ORDER BY a.SUM查询出成绩六到十名
SELECT * FROM (...) b ORDER BY b.SUM DESC将结果倒序按照从高分到低分排列*/
12. 查询各科成绩的前三名以及分数
[sql]
SELECT
s.Sid,s.Cid,s.Score
FROM
SC s
WHERE
s.Score
IN
(
SELECT
TOP
(3) Score
FROM
SC
WHERE
s.Cid= Cid
ORDER
BY
score
DESC
)
ORDER
BY
s.Cid;
/*从SC表中查询出学生学号，课程编号以及成绩，WHERE子句限制了查询出的记录成绩必须在子查询集合内
子查询查询出了各科成绩的前三名并通过课程编号和主查询关联*/
13. 查询有不及格科目的学生的姓名，不及格科目以及不及格科目成绩
[sql]
SELECT
s.Sname,c.Cname,ss.Score
FROM
Student s
JOIN
SC ss
ON
s.Sid=ss.Sid
JOIN
Course c
ON
ss.Cid=c.Cid
WHERE
ss.Score<60
14. 查询所有学生都选修的课程
[sql]
SELECT
c.Cname
FROM
SC s
JOIN
Course c
ON
s.Cid=c.Cid
GROUP
BY
c.Cname
HAVING
COUNT
(s.Sid)=(
SELECT
COUNT
(*)
FROM
Student)
15. 查询选修了两门或以上的学生姓名及选修总科目
[sql]
SELECT
s.Sname,
COUNT
(ss.Cid)
AS
TOTAL
FROM
Student s
JOIN
SC ss
ON
s.Sid=ss.Sid
GROUP
BY
s.Sname
HAVING
COUNT
(ss.Cid)>1