rank()和dense_rank()
https://blog.csdn.net/yangshangwei/article/details/53038325
start with...connect by子句
https://blog.csdn.net/weixin_30295091/article/details/96089776
rollup()函数
https://blog.csdn.net/mxmxz/article/details/51751209
ROW_NUMBER()
ROW_NUMBER() OVER(partition by col1 order by col2) 表示根据col1分组，在分组内部根据col2排序，而此函数计算的值就表示每组内部排序后的顺序编号（组内是连续且唯一的）。
https://blog.csdn.net/iw1210/article/details/11937085
转义字符
https://blog.csdn.net/Adi_liu/article/details/1920606
实例
一、查询没学过“谌燕”老师课的同学，显示（学号、姓名）
SELECT hs.student_no,
hs.student_name
FROM hand_student hs
WHERE NOT EXISTS (SELECT 1
FROM hand_course hc, hand_teacher ht, hand_student_core hsc
WHERE hc.teacher_no = ht.teacher_no
AND hc.course_no = hsc.course_no
AND ht.teacher_name = '谌燕'
AND hsc.student_no = hs.student_no);
二、查询没有学全所有课的同学，显示（学号、姓名）
SELECT hs.student_no,
hs.student_name,
COUNT(hsc.course_no)
FROM hand_student hs,
hand_student_core hsc
WHERE hs.student_no = hsc.student_no(+)
GROUP BY hs.student_no, hs.student_name
HAVING COUNT(hsc.course_no) < (SELECT COUNT(hc.course_no) FROM hand_course hc);
---------------------------------------
SELECT hs.student_no,
hs.student_name
FROM hand_student hs
WHERE hs.student_no in
(SELECT student_no
FROM (SELECT hs.student_no, hc.course_no
from hand_student hs
CROSS JOIN hand_course hc
MINUS
SELECT hsc.student_no,
hsc.course_no
FROM hand_student_core hsc));
三、查询“c001”课程比“c002”课程成绩高的所有学生，显示（学号、姓名）
SELECT hsc1.student_no,
hs.student_name
FROM (SELECT * FROM hAND_student_core sc1 WHERE sc1.course_no = 'c001') hsc1,
(SELECT * FROM hAND_student_core sc2 WHERE sc2.course_no = 'c002') hsc2,
hand_student hs
WHERE hsc1.student_no = hsc2.student_no
AND hsc1.core > hsc2.core
AND hsc1.student_no = hs.student_no;
---------------------------------------
SELECT hsc.student_no,
hs.student_name
FROM hand_student_core hsc,
hand_student hs
WHERE hsc.student_no = hs.student_no
AND hsc.course_no = 'c001'
AND EXISTS (SELECT *
FROM hAND_student_core hs
WHERE hs.course_no = 'c002'
AND hs.core < hsc.core
AND hs.student_no = hsc.student_no);
四、按各科平均成绩和及格率的百分数，按及格率高到低顺序，显示（课程号、平均分、及格率）
SELECT hsc.course_no,
AVG(hsc.core) avg_core,
(SUM(CASE
WHEN hsc.core >= 60 THEN
1
ELSE
0
END) / COUNT(*) * 100) || '%' AS pass_rate
FROM hand_student_core hsc
GROUP BY hsc.course_no
ORDER BY pass_rate DESC;
五、1992年之后出生的学生名单找出年龄最大和最小的同学，显示（学号、姓名、年龄）
SELECT hs.student_no,
hs.student_name,
hs.student_age
FROM hand_student hs,
(SELECT MAX(hs.student_age) max_age,
MIN(hs.student_age) min_age
FROM hand_student hs
WHERE to_number(to_char(SYSDATE, 'yyyy')) - hs.student_age > 1992) hh
WHERE hs.student_age = hh.max_age OR hs.student_age = hh.min_age;
六、统计列出矩阵类型各分数段人数，横轴为分数段[100-85]、[85-70]、[70-60]、[<60]，纵轴为课程号、课程名称
SELECT hsc.course_no,
hc.course_name,
SUM(CASE
WHEN hsc.core BETWEEN 85 AND 100 THEN
1
ELSE
0
END) AS "[100-85]",
SUM(CASE
WHEN hsc.core BETWEEN 70 AND 85 THEN
1
ELSE
0
END) AS "[85-70]",
SUM(CASE
WHEN hsc.core BETWEEN 60 AND 70 THEN
1
ELSE
0
END) AS "[70-60]",
SUM(CASE
WHEN hsc.core < 60 then
1
ELSE
0
END) AS "[<60]"
FROM hand_student_core hsc,
hand_course hc
WHERE hsc.course_no = hc.course_no
GROUP BY hsc.course_no, hc.course_name;
七、查询各科成绩前三名的记录:(不考虑成绩并列情况)，显示（学号、课程号、分数）
SELECT student_no,
course_no,
core
FROM (SELECT hsc.student_no,
hsc.course_no,
hsc.core,
DENSE_RANK() OVER(PARTITION BY hsc.course_no ORDER BY hsc.core DESC) ranks
FROM hand_student_core hsc)
WHERE ranks < 4;
八、查询选修“谌燕”老师所授课程的学生中，成绩最高的学生，显示（学号、姓名、课程名称、成绩）
SELECT hs.student_no,
hs.student_name,
hc.course_name,
hsc.core
FROM hand_student hs,
hand_student_core hsc,
hand_course hc,
hand_teacher ht
WHERE hs.student_no = hsc.student_no
AND hsc.course_no = hc.course_no
AND hc.teacher_no = ht.teacher_no
AND ht.teacher_name = '谌燕'
AND hsc.core = (SELECT MAX(sc.core)
FROM hand_student_core sc
WHERE sc.course_no = hc.course_no);
九、查询两门及以上不及格课程的同学及平均成绩，显示（学号、姓名、平均成绩（保留两位小数））
SELECT hsc.student_no,
hs.student_name,
ROUND(AVG(hsc.core),2) avg_core
FROM hand_student_core hsc,
hand_student hs
WHERE EXISTS (SELECT sc.student_no
FROM hand_student_core sc
WHERE sc.core < 60
AND sc.student_no = hsc.student_no
GROUP BY sc.student_no
HAVING COUNT(sc.student_no) > 1)
AND hsc.student_no = hs.student_no
GROUP BY hsc.student_no,hs.student_name;
十、查询姓氏数量最多的学生名单，显示（学号、姓名、人数）
SELECT hs.student_no,
hs.student_name,
ht.cnt
FROM (SELECT SUBSTR(hs.student_name, 1, 1) surname,
COUNT(1) cnt,
dense_rank() OVER(ORDER BY COUNT(1) DESC) ranks
FROM hand_student hs
GROUP BY SUBSTR(hs.student_name, 1, 1)) ht,
hand_student hs
WHERE SUBSTR(hs.student_name,1,1) = ht.surname
AND ht.ranks = 1;
十一、查询课程名称为“J2SE”的学生成绩信息，90以上为“优秀”、80-90为“良好”、60-80为“及格”、60分以下为“不及格”，显示（学号、姓名、课程名称、成绩、等级）
SELECT hsc.student_no,
hs.student_name,
hc.course_name,
hsc.core,
CASE WHEN hsc.core >= 90 THEN
'优秀'
WHEN hsc.core < 90 AND hsc.core >= 80 THEN
'良好'
WHEN hsc.core < 80 AND hsc.core >= 60 THEN
'及格'
WHEN hsc.core < 60 THEN
'不及格'
END core_level
FROM hand_student_core hsc,
hand_course hc,
hand_student hs
WHERE hsc.course_no = hc.course_no
AND hsc.student_no = hs.student_no
AND hc.course_name = 'J2SE';
十二、查询教师“胡明星”的所有主管及姓名:（无主管的教师也需要显示），显示（教师编号、教师名称、主管编号、主管名称）
SELECT ht1.teacher_no,
ht1.teacher_name,
ht1.manager_no,
ht2.teacher_name manager_name
FROM hand_teacher ht1,
hand_teacher ht2
WHERE ht1.manager_no = ht2.teacher_no(+)
START WITH ht1.teacher_name = '胡明星'
CONNECT BY PRIOR ht1.manager_no = ht1.teacher_no;
十三、查询分数高于课程“J2SE”的所有学生课程信息，显示（学号，姓名，课程名称、分数）
SELECT hsc.student_no,
hs.student_name,
hc.course_name,
hsc.core
FROM hand_student_core hsc,
hand_course hc,
hand_student hs
WHERE hsc.course_no = hc.course_no
AND hsc.student_no = hs.student_no
AND hsc.core > ALL (SELECT hsc.core
FROM hand_student_core hsc,
hand_course hc
WHERE hsc.course_no = hc.course_no
AND hc.course_name = 'J2SE')
AND hc.course_name != 'J2SE';
十四、查询教师、课程及选课的学生数量：(使用rollup),显示（教师名称、课程名称、选课数量）
SELECT ht.teacher_name,
hc.course_name,
COUNT(1) nums
FROM hand_student_core hsc,
hand_teacher ht,
hand_course hc
WHERE hsc.course_no = hc.course_no
AND hc.teacher_no = ht.teacher_no
GROUP BY ROLLUP(ht.teacher_name,hc.course_name);
十五、查询所有课程成绩前三名的按照升序排在最开头，其余数据排序保持默认（7分）,显示（学号、成绩）
SELECT hs.student_no,
hs.core
FROM (SELECT rownum rn,
hsc.student_no,
hsc.core,
row_number() OVER(ORDER BY hsc.core DESC) ranks
FROM hand_student_core hsc) hs
ORDER BY CASE WHEN ranks <= 3 THEN -ranks ELSE null END,rn;
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