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='004') AS 数据库,
(SELECT grade FROM t_score WHERE sid=t.sid AND cid='001') AS 企业管理,
(SELECT grade FROM t_score WHERE sid=t.sid AND cid='006') AS 英语,
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 )
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
SELECT t1.cid As 课程ID,t1.grade AS 最高分,t2.grade AS 最低分
FROM t_score t1 , t_score t2
WHERE t1.cid = t2.cid
and t1.grade = (
SELECT MAX(tt1.grade ) FROM t_score tt1,t_student tt2
WHERE t1.cid = tt1.cid and tt2.sid = tt1.sid
GROUP BY tt1.cid
)
AND t2.grade = (
SELECT MIN(tt3.grade ) FROM t_score AS tt3
WHERE t2.cid = tt3.cid GROUP BY tt2.cid
);
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
SELECT t.cid AS 课程号,max(course.cname)AS 课程名,isnull(AVG(grade ),0) AS 平均成绩 ,
100 * SUM(CASE WHEN isnull(grade ,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数
FROM t_score t1,t_course t2
where t1.cid = t2.cid
GROUP BY t1.cid
ORDER BY 100 * SUM(CASE WHEN isnull(grade ,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC
20、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理（001），马克思（002），OO&UML （003），数据库（004）
SELECT
SUM(
CASE WHEN cid = '001'
THEN grade ELSE 0 END)/SUM(CASE cid WHEN '001'
THEN 1 ELSE 0 END
) AS 企业管理平均分 ,
100 * SUM(
CASE WHEN cid = '001' AND grade >= 60
THEN 1 ELSE 0 END)/SUM(CASE WHEN cid = '001'
THEN 1 ELSE 0 END
) AS 企业管理及格百分数 FROM t_score
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 ;
22、查询如下课程成绩第 3 名到第 6 名的学生成绩单：企业管理（001），马克思（002），UML （003），数据库（004）
[学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩
SELECT DISTINCT top 3 t_score.sid As 学生学号,Student.Sname AS 学生姓名 ,
T1.grade AS 企业管理, T2.grade AS 马克思, T3.grade AS UML,
T4.grade AS 数据库,ISNULL(T1.grade ,0) + ISNULL(T2.grade ,0) + ISNULL(T3.grade ,0) + ISNULL(T4.grade ,0) as 总分
FROM Student, t_score
LEFT JOIN t_score AS T1
ON t_score.sid = T1.sid AND T1.cid = '001'
LEFT JOIN t_score AS T2
ON t_score.sid = T2.sid AND T2.cid = '002'
LEFT JOIN t_score AS T3
ON t_score.sid = T3.sid AND T3.cid = '003'
LEFT JOIN t_score AS T4
ON t_score.sid = T4.sid AND T4.cid = '004'
WHERE student.sid= t_score.sid
and ISNULL(T1.grade ,0) + ISNULL(T2.grade ,0) + ISNULL(T3.grade ,0) + ISNULL(T4.grade ,0)
NOT IN (
SELECT DISTINCT TOP 15 WITH TIES ISNULL(T1.grade ,0) + ISNULL(T2.grade ,0) + ISNULL(T3.grade ,0) + ISNULL(T4.grade ,0)
FROM t_score
LEFT JOIN t_score AS T1
ON t_score.sid = T1.sid AND T1.cid = 'k1'
LEFT JOIN t_score AS T2
ON t_score.sid = T2.sid AND T2.cid = 'k2'
LEFT JOIN t_score AS T3
ON t_score.sid = T3.sid AND T3.cid = 'k3'
LEFT JOIN t_score AS T4
ON t_score.sid = T4.sid AND T4.cid = 'k4'
ORDER BY ISNULL(T1.grade ,0) + ISNULL(T2.grade ,0) + ISNULL(T3.grade ,0) + ISNULL(T4.grade ,0) DE t_score
);
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 avggra